I guess it also depends on the individual. There are women who love the feeling and anal is a part of their sex routine. An ex-girlfriend of mine was an absolute anal freak, like Adriana Chechik level. There were literally times were my dick was sliding up her ass accidentally and I couldn't tell the difference. No prep, no lube, just body fluids and she could take it all night long in every possible position.Hmmm I guess I never thought of it that way, when she allows me to do it it doesn’t require a ton of prep
The great percentage of women though are not like this, and this is why prep is essential.