Why is it that on a lot of manga/doujin You see yuri acts on the front and there is not any in the doujin itself (aka please link me a few of the better yuri doujins if you wouldnt mind) This might be my first post if not one of my first So HI :D
Their might also be two seperate storylines with two different girls. They put the two main girls on the cover together to show you who is in the manga.
Doujin like naruto with Sakura, Temari, Ino, and Hinata come to mind. They might not have sex scenes together, but they are both in the doujin so they are both on the cover to let you know "hinata AND sakura are in here."
This is one of my favorites, not story wise but artwise. Plus it has to girls on the cover (not yuri scene though :() so it kinda relates to what we were talking to. Sakura and Temari
It's for instant appeal to the buyer since, admit it, doujin/manga buyers are mostly guys. Selling point psychology, IMO. Putting the most fuckable bitches on the cover makes the buyer instantly know what he's getting for faps (as razama pointed out above, TY).
Also, if you're subconsciously getting the "yuri" feeling for the pairing, remember that some yuri works are male-targeted, and some of it as influence is carried over to the manga covers. The creators' point is that if you get "that yuri" feeling, they succeeded with making the cover appealing. The one razama linked for Sakura and Temari has this cover that they look like a yuri couple, but they are not. Some guys are appeased by these types of visuals that pair girls (the Nosebleed section gives that feel as well).
EDIT: Woops, gomen ne. I meant the Nosebleed section for yuri.
Yeah, I've have always wondered just that. If yuri sells then why isn't it filled whit yuri inside? The inner content suggest most doujin artists are more into hetero, real question is, why aren't they more into yuri? Yuri owns!