No, seriously. Why? You mean to tell me that in all the years of arcane study a couple of wizards never stopped and went:
Wizard A: Hey, you ever notice how those Holier-Than-Thou divine casters can cast healing magics?
Wizard B: Yeah...?
Wiz A: Well why cant we do that?
Wiz B: Dunno? Cuz nobody ever researched it I suppose...
Wiz A: Well why the crusty beard of the Pit not?
Wiz B: Dunno...
Wiz A: You think we should?
It makes no sense! You mean to tell me that a wizard of appropriate level can rearrange the very fundamentals of a creatures being but he cannot knit a gash without having a cleric nearby? I can assume the rest of that conversation went something like this:
Wiz B: ... Naw, those guys seem to have the heally bit well in hand... And we have to get this new and improved "Fiery Doom of Conflagratory Destruction" finished.
The Arcane Disciple feat grants an Arcane Caster access to one domain's worth of spells. Healing Domain has most of the Cure + Heal.
Planar Handbook allows any caster to swap the ability to summon either Fiendish or Celestial creatures with Summon Monster spells for the ability to summon Vivacious creatures. A Vivacious creature has a positive energy aura which heals all living creatures within 10 ft 1 point per round. It also has an "attack" which deals 1d4+cha positive energy damage (living creatures are healed by positive energy damage) usable every 1d4 rounds.
A Warforged party can be healed via the Repair Damage line which are on the Sor/Wiz list.
10 levels of Rainbow Servant grant access to the whole Cleric list. An option for any arcane caster but it works best for Warmages and Beguilers because they can spontaneously cast any spell on their list.
The Prestige Bard class from Unearthed Arcana grants access to the Bard list to other classes that meet the requirements.
An obscure class from Dragon Compendium, the Sha'ir can cast some domain spells as divine spells. This means it can qualify for divine Prcs. Skypledged grants access to a divine spellpool ability which includes healing.
Various arcane classes have UMD and Wand of Lesser Vigor is one of the best out of combat healing options around.
If Artificers count as an arcane casting class, they have a number of healing Infusions.
Most of that is convolution. Further, it is either negative energy, which is harmful in most campaigns, reliant on multi-classing or a prestige class, using / wasting a feat, or summoning a creature and not reliant on the caster's own ability. In most of those cases it is still reliant, arguably, on an amount of divine casting. On top of this, none are immediately useful. That is to say, no arcane class has easy access to healing magics.
As for the Sha'ir, Dragon magazine is seldom a place one goes for anything as recognizably sound...
Which is a nice way of saying all the DMs I know will go:
"Where's it from?"
"NOT IN MY GAME!"
Pathfinder's Witch is an arcane class capable of healing ninja
You know, I haven't paid much attention to the witch...
I tip good avi's by the way.
bards do so count, they cast arcane magic(wizard) and divine magic(cleric) boom!
you can multiclass too
Multiclassing is convolution and difficult to retain effectiveness. And the reason I say bards don't count is as a class they are largely... I suppose the word is aimless. The spells they do get they get beyond the point when they are decently useful.
Game balance. Bards count.
I loathe those words... They are the guise of a lazy and uncreative mind.
That's why Chaos 6010 has a number of methods of healing, was because of this pitfall noticed in that few players ever wanted to play "the healer" or "the cleric".
Instead, the spells were divided into the various "colors", and all casting classes have access to all spells. Red is destruction and energy, White is healing and protection, Gray is mind affects, Black is necromantic, Blue is detection and sensory, and Green is elemental.
The differences between classes is what spells they begin with, and what abilities they pick up each level. In theory, a Shaman, a Mage, a Priest, and a Technomancer can all have the same spells, but be played completely different due to the character customization inherent in the system.
My group have had bard healers a lot we always manage fine, sure they aren't as efficient as a cleric, but if you want efficient then you have to sacrifice roleplaying ability as in my experience roleplaying a character with flaws and dreams and goals, is rarely efficient.
And all that being said as was previously stated, there is the witch, who not only has the spells and gets them at wizard levels, but can take the healing hex, healing patron and the healing archtype (I think its hedge witch). But the witch loses a lot of direct damage spells and is more about versatility then anything else. The only issue is if your playing 3.x and not Path and even then there is a witch class half built in the DMG so speak with the GM about it.
You may not like the use of game balance as a reason but its used cause otherwise you'd never have a cleric/oracle as the wizard could do their job and his job at the same time. And I don't find it hard to believe that arcane magic couldn't heal since I think every wizard spells that heals either takes it from another target or its temporary HP. Maybe you'd have a nice GM that would say you could research it, but as far as I can remember Divine was the only power source that offered straight healing, as Psionics I believe you transferred the wounds to a foe or from a friend.
I know of a couple of games/books/shows that allowed 'wizards' to heal but usually they could heal but do no real damage, its swings and round abouts, and those that focus on healing would be unlikely to decide that they also wanted to rain fire and comets from the sky.
... but if you want efficient then you have to sacrifice roleplaying ability as in my experience roleplaying a character with flaws and dreams and goals, is rarely efficient.
Clearly you've never met any of my clerics. Every one of them is an efficient healer AND a joy to roleplay with their own unique flaws and goals. Just because I optimize my character build doesn't mean I can't roleplay with it.
Wizards, by the rules of D&D 3.5, can technically cast Cure spells. You simply have to spend the time, in character, to do the research. I couldn't tell you a real reason why Wizards don't have access to healing other than to say maybe they tried, and it never worked out. False Life could have been an attempt at a healing spell that didn't quite work out.
Just because a character is optimized doesn't mean that they cannot be role played. Just the opposite, in fact, as characters really great at a few focused things are often exceedingly inept or weak at other things. It is overcoming weakness that spins the greatest stories.