Just think of nudity as acting without clothes on, if that makes it more palatable.
I have to echo other people's comments. Franco's films are dreamlike and surreal. Yes, there's often nudity, but it's placed in such an odd way it just adds to the surrealism. It's not traditional nudity, as in sex scenes. Quite often people just pop up with no clothes on, there's no sex and they contribute dialogue. It's quite strange but give Franco's films a flavour quite unlike that of any other director, except for perhaps Rollin. In fact, I think Franco's films deal more in subversiveness and sexual tension than outright erotica. There's a definite philosophy behind what Franco does.