Definitely not pointless. It actually fills a dual role. It gives entertainment value for the fans who want that, and legitimacy to the fans who wish that rankings mattered. I've read a few posts here sayings that rankings matter, but do they? If that were the case, would anyone unranked fighter bc challenging for the HW belt? A tourney settles the matter. The two most deserving fighters fight in the final.
As far as getting them to actually fight and stay in, it's apparent that they'd give handsome locker room bonuses to the fighters who make it so far.
And, the tourneys don't have to play out for months and months either. One card for quarterfinal, semis and final can be held three or four months later on the same card. This is possible, bc Bellator has been doing that.
Tournament format is not stupid, BTW. There are an enormous amount of fans who adore the format and wish for it's return. It is realistically the best way to decide who the best is, bc the ranking system is flawed, it doesn't take much to see that.