I have no idea why you would assume it would only be done anally...
Obviously it could be done vaginally or anally, just like normal sex.
Every sexual act that turns someone on is vile to someone else. Including regular old sex
@someone like u-while I cannot speak from personal experience the way I understand it is your vagina (or anus) does have to become more flexible (not loose) to be able to handle fisting, but the vagina is a muscle just like any other muscle. People who are very fit and very flexible don't have loose saggy muscles, quite the opposite actually. They are able to stretch more due to their flexibility, but they are not loose.
If that makes sense.
Loose is lack of muscle tone and lack of ability to grip. Flexibility is ability to stretch.