That's actually a damn good question--and I think the bigger bitcoin "projects" like hardware wallets don't need to advertise on a discussion forum, which honestly seems like an outdated method of drumming up business. 

Bitcointalk, for as long as I've been here, has been full of gamblers and gambling is and has been one of the biggest uses of bitcoin I know of, aside from the dark web (and I don't even know what the stats are on that).  I assume that's why there have been so many gambling-related signature campaigns.  They might rake in a lot of cash, but I think compared to other businesses they're fairly small-time and don't have to shell out enormous amounts of money to hire a bunch of forum posters.  Like I said, good question you're asking here.  After the caffeine hits my bloodstream perhaps I might give it some more thought.