I've always thought trainers were more for accountability and motivation as opposed to someone actually needing help figuring out how to work out. A large percentage of the population won't do anything unless someone is right behind them telling them to do it. Its literally how we were all taught to learn in school.
I agree I just find it such a waste of time if you arent being trained by a specialist...for some special shyt. Got people getting trained on the doing the most basic of shyt making zero progression. I think most just like the social aspect and if they are using a trainer they can feign like they are doing something. Not to say some trainers are cold, but for the most part google is your friend.