They do...but most also pay delegators with smt’s, which might be worthless at the moment but when they are finally launched (they will at some point) some will have substantial value.
At the moment it is just accumulation...in a few months apps will be more profitable
I agree, and wrote on this very recently; that groups will develop that will take the profts available from the blockchain and redistribute them according to their own criteria.
If the core economic model of Steem does not change, then this will be the next development.