My first serious GF loved anal. GF's after that either were short term GF's or didn't even want to try it.
I think the negativity is based on fear, mostly. Maybe a guy before you slammed it up her ass like a porn dude does, completely ignoring the fact that the porn gals prepare ahead of time. Too many pornos have the guy doing it without lube. That's BS, and asking for a woman (unless she's actually into that, particularly) to swear off anal forever.
With some it may be concerns about cleanliness. That can be overcome by education and preparation, but not all couples are into that, either.
Some of it just might think it's perverted. There are a lot of obstacles, especially if the woman is over 35 or so. The younger women are more into it, because porn has made it more acceptable as a form of sex, and I think the younger people are more educated about anal than the older demographics are, generally.
To me anal is fun. But if a woman doesn't want to do it, it's not a deal breaker, as long as the rest of the sex is good. I still like to use a finger in a woman's ass now and then, and if a woman won't even let me use a lubed finger there it doesn't score a lot of points with me, because I love the feel of it on my finger when licking her pussy. But the sex in general is more important to me. If the rest of it is good and hot, lack of anal play is not that great a loss.