My take on it is some tokens that are pre-mined still have a blockchain model thru which they function, so their value proposition is not thru mining and that might limit some optios, however companies still find ways to incentivize processing power via alternative programs where you become a node for a non-mined tx fee that you get paid. I think that's how witnesses work in both bitshares and Steemit, but I haven't gone through their whole documentation. Neo generates gas for holders of it, even though it's pre-mined. I don't know how they strengthen their network but that's the same answer, I've yet to read their whole documentation.