It's back to the skill vs luck debate
With the usual caveat that I have never attended a live tournament in my life, ....
Slot machines are more popular still, but you wouldn't expect slot tournaments to rival poker tournaments in popularity. Surely the fundamental difference between poker and BJ lies in the mindset of the vast majority of players.
Everyone knows that poker is a game in which you attempt to beat the other players, while BJ is you against the house, with the house having the best of it. It requires no great mental leap to switch from the idea of a poker cash game to a poker tournament.
With BJ, on the other hand, it's not immediately obvious (even to people who know something about BJ, let alone the majority of recreational gamblers) that it is possible to take on other players and develop skills that can give you an edge. I think most people, coming across the concept for the first time, would see BJ tournaments as a total game of chance.
As for the duration of the events; with more people attending, plus the inherent open-endedness of poker compared to BJ (i.e. you keep playing until someone has all the chips) poker probably lends itself more to long, drawn out events. Plus, if only a few dozen people are likely to be even considering turning up to a BJ event then the longer it is, the less likely they can all attend for the whole time.
