I think role BP bonuses are one of the biggest band-aid fixes in DBD history.
If there are way more people playing one side than the other, then it shows there is an issue with your game itself. It doesn't matter if it's "more balanced." In any game, especially a more casual game such as this, fun takes priority.
And when one role in your game is so unfun, and your game's grind is so unfun, that you need to provide bonuses, that shows a massive problem. Killer queues have been upwards of 10 minutes for most regions, and nothing is being done to address it other than this horrible band-aid.
Personally, I think it's insulting that they're dangling BP in our face for playing the role we don't enjoy. Fix the core game.