Because less people play DOA, everyone and their mother owns Tekken since its a more popular franchise but I think 1/6 of the people who bought Tekken 7 the first week bought DOA6. And I hope we don't get another release of DOA6 since it'll be a DOA5 situation all over again. I think once the Character DLC begins pouring in more people will get into it again
That's pretty much what's going to happen...
People are going to show up again regardless to see how Mai and the other KOF character translates to DOA6 and by that time hopefully all of the kinks are finally ironed out by that point.
It also helps that regardless of DOA6's issues, people are still genuinely hyped over DOA World Championship and want it to succeed.
There's alot to not be happy about with DOA6, but I do feel that continuing the air of cynicism and negativity with no real outlet just creates a bad spiral all-around. And no, I'm not saying don't criticize KT or TN still having issues creating lobbies or crap like that, I'm saying that being constantly doomsaying helps no one and just keeps the cycle of negativity flowing.
It's easier to be negative than it ever is to be positive.