What if you just happen to enjoy steak and your friend enjoys chicken? Then in the 50-50 split, you could be seen as "abusing" the system if you two go out to dinner often, yes?
A 50-50 split is never how it works out - you look at the bill and think "X spent about £15 and Y spent about £20, so we'll put that down and then make up the change between us". Or "let's split the food 50-50 and I'll get the drinks".