This is the really disappointing thing about a lot of yuri out there. It has more thought put into it than your average h-manga and more often than not has an interesting premise, but there's never any real emphasis on the sex or physical intimacy and it gets cut way too short to be close to satisfying.
I guess futa is the closest thing you get to hit all the notes when it comes to girl-on-girl, but it's kinda disappointing since yuri has most of the intriguing ideas in hentai.