Also think that making a bounty is the "cheapest" way to promote a project, although not all teams do. If a project is really new and innovative, there are companies that invest directly in those projects, and only with that its popularity multiplies. The last time I saw it, Pantera Capital was the investor, and the project flew to the moon. But it is not easy for Pantera Capital to be interested in a project, it must be something really good.
The options are not many, the cheapest and easiest thing is to make a bounty, the teams that do not do it are very sure of their project or perhaps they are not clear about what they are doing. What is not planned today will be a problem tomorrow.