Well, it depends...for most other TV shows, I'd say the ratings shouldn't matter that much, especially when they're threatening to cancel good shows that don't do well in the ratings, but have a huge following anyway (Community). In that area, the ratings are flawed because we, the viewer, are now able to decide when WE want to watch the show and are not limited to when the network thinks we should watch the show (which is actually part of my theory as to why shitty shows are so popular...because it's fan base doesn't understand that they can watch their show online because watching shows on the computer is still an idea in its infancy). However, even though wrestling is a scripted show just like many other shows, I feel it also runs like a sports program. I don't think many people wait to watch games that have already happened (unless something interesting happened...and then they may just watch the highlights). So for a wrestling company, the ratings are more important than for regular TV, because if you're not convincing people to watch your show when it airs, you're most likely not convincing them to watch it at all.
But how does that relate to us? Not too much actually. There have been several episodes of RAW where I've gone "Wow, that was actually a good episode for once" and the ratings came out and didn't reflect the quality. Now obviously, I'm not going to change my mind on what I thought of the show...but I'm sure WWE is looking at it going "well, CM Punk isn't bringing up ratings...we should probably move him aside for Cena." And that's where the ratings start to affect what we, the viewers, get to see.
And then you have something like TNA...where the ratings have been the same junk for years now (even before Hogan and Bischoff). And all the while people are telling them "we don't want to watch this crap," they ignore us and keep putting out the same s**t over and over and over and over again. A company that just blatantly ignores what its fans are saying, especially when the fans want the product to be better so that there is a true alternative to televised wrestling, reflects badly on the product...and the ratings continue to show that.