Anal stretching

Question, Why is anal stretching for some women so interesting? Using large dildos even stretching using hands and arms sometimes both hands both arms completely up to the elbows. I can’t imagine it’s doing the intestines any good. Can anybody answer this for me of course I’m a male, but I can’t imagine someone sticking their fist and arm halfway up my bodie. and don’t think I’ll try.
Thanks Butch