I was adopted as a kid, but am also in contact with my biological family (the full story is long and dull.) I have a biological child and would be fully willing to adopt, though I have not yet.
So I feel like I can speak with some if not full authority on the subject.
There is a difference between an adopted child and a biological child. There is a difference between an adopted parent and a biological parent.
Taking on a child, any child, whether biological or adopted, is an enormous responsibility. Some people are not up for that responsibility and shouldn't have children. Other people are not up for having biological children--for whatever reasons, either they don't want to go through pregnancy or they have a genetic condition or they're unable to do so--but they believe they will be good adoptive parents. Some people even believe it is noble to adopt, and so want to do so.
By contrast, other people would not make good adoptive parents. When people say, 'an adopted child is not the same as a biological one,' aside from this being true on a biological level, it's also true on a mental level. Many parents would not be physically capable of loving an adopted child the way they could a biological child (or at least they believe so.) The process by which we fall in love with our children is complex and fundamentally biological, especially so for mothers, who normally gestate and nurse their children. Nature has provided a complex feedback cycle to make us love and care for our genetic offspring. Nature has provided us with the tools to care for other people's offspring basically as an accidental side-effect of our tools for caring for our own children and our relative's children.
In other words, most people will instinctively love their biological children, because that is how we are wired. People are not pre-wired to love a random child who happens to show up in their midst. People instinctively want to pass on their own genetics to the next generation. That is the crux of all reproduction, after all. People have little instinctive impulse to spend their time and resources helping someone else's genetics survive--in fact, such people get quickly bred out of the gene pool.
While that is a somewhat cynical and less than romantic way of looking at things, when you come down to the individual, they're not generally thinking 'Nooo I don't want to waste my resources, I want to pass on my genes," they're thinking, "But I want to have MY baby. I don't want to have someone else's baby." And try as you might to reason with them, they will always experience biological and adopted children differently. They will be physically unable to love a biological child like an adopted child, and will feel the loss of the relationship they didn't have.
As an adopted kid, I love my adopted dad, but I love my biological dad more. I 'connect' with him in ways that I don't with my adopted dad, even though I was around my adopted dad more during my childhood and we're actually culturally more similar. There are just things about my biological father and I which I don't share with my adopted family and which they therefore can't understand. It's a different connection. A different relationship.
To a person having trouble conceiving, the idea of not having a biological child can be absolutely crushing. It's not just that adopted children are different, but that they are unable to produce the children they want. They have to give up. They failed. They have to accept a child who may never see them as a 'true' parent, a child who is more likely to have mental and physical disabilities and issues, a child who will not be like them and whom they will not connect with on an intuitive level the way you can with a biological child.
And that is why mentioning adoption is considered taboo. Because people are fragile and going through a difficult time and the idea of adoption is tantamount to failing and having to accept an inferior relationships.
(Additionally, some people *can't* adopt. My step father, for example, was deemed too old to adopt. However, with fertility treatments and lots of effort, he and his wife managed to conceive and so I have a step sister who's 18 years younger than me.)
200
50
100
100
100
150
500
300
400
