Is it that big of a taboo? As big of one as interracial relationships or body modifications. Back in the day, yes. Nowadays (depending on where you live), who the hell cares?
Why would anyone want to do it? Why else would anyone want to do anything they find to be pleasurable? Because those who do it find it pleasurable…
It would…
1) Hurt immensely. To some, yes, indeed, there is some amount of pain involved. Some try it and don’t like the pain associated with it. Therefore, they never try it again. Others work past it and find the light at the end of the long, dark tunnel…
2) Would be gross. Subjectively speaking, what else is and is not gross? I think eating seafood/shellfish is gross. Others dont. Therefore, I dont have to eat their seafood – more seafood for them, then. Same rule applies.
3) Why would anyone want to stick something up there anyway? Why would anyone want to go bungee jumping, scuba diving, sky diving, circuit racing, hang-gliding, motorcycling or do anything else that most people would agree you have to take a serious risk with your life to attempt? Maybe I’m comparing apples to oranges here, but the point is that people have their preferences as far as thrills, hobbies and leisure activities go. For some, it’s bungee jumping. For others, it’s anal sex. Not everyone is going to agree that the same activity is fun for everyone, across the board. For instance, riding a roller coaster probably isn’t going to be a fun activity for my 80-something year old grandfather, but a more than exhilarating time for my 15 year old cousin.
You run the obvious risks (as you do with performing any kind of sexual acts with anyone) and as long as the people participating are pretty hygienic about it, you wont end up with any “gross” stories to tell.
I’m not understanding why anyone would like it… Probably because you’re under the impression that if you dont enjoy something, other people should or would not. I beg to differ, it’s actually quite the contrary.