There are two sides to this coin budgie and I'm afraid I think some coaches need to put their own personal ambitions and desire to win to one side and remember that it's a kids game.
It's true that there are a few like that around, but the vast majority are just parents/volunteers trying to provide cheap or free sports opportunities for children.
However, in the leagues in which my DSs play, up until age 11 the leagues are non-competitive, with scores not being recorded. But from the age of 11 the leagues become competitive, with placings and league winners. There are 4 pools, and teams are moved up and down the pools according to their places from the previous season.
So I can certainly understand why a coach would want to enter a strong team. Not a 'win at all costs' mentality , but it makes sense to have a core of stronger players, and rotate the weaker players. And unfortunately there are occasionally players who just do not have the ability to play at a certain level. Against much stonger opposition it can, at best, be demoralising for a weak player , at worst, it can be dangerous as children get older and more physical.
It can be a difficult and thankless task for the coach to get the balance of competiveness and inclusion right. And, believe me, a coach can never please all the parents all the time.