I completely agree. A good boss would likely appreciate a union, because the kinds of minor concerns that might be raised at a meeting are the kinds of things that individuals wouldn't mention because it's not worth the stress to flag it - even under a good boss who you trust would take even minor concerns seriously, it still costs time and brain energy to raise a thing, and the union being the middle man between the boss and the worker can be a boon in terms of collating concerns.

Not least of all because one of the concerns may be about a thing that is genuinely too trivial to make a thing of, if it's only affecting one person. A union has the ability to go "hey, so this is only a small thing but a few people have mentioned it to us and we went around asking and it does seem quite widespread"