I can only speak for our situation. My son who signed his baseball NLI came very close to skipping his senior year this year because his coach is one of the bad ones. I hope bad coaches are rare but for his high school he is one for one. It's worse now that he has played for some top flight summer and college coaches and can really see the problem.Kids quit in droves and the team consequently is always at the bottom. I think he is just playing so he can rub it in as much as he can, I.E. "I, who you treated with disrespect and rudeness am now going to play in college while your kid and his friends who you always gave the gravy to are playing their last year ever"
I think it will be fun for him and maybe open up this coaches eyes that you can't write kids off that are sitting on your bench but actually might be more talented than you think and maybe you are not the judge of talent you think you are. The sad thing is all the ones that quit.
Haveing coached for many years it's not that hard to make guys want to return even if they are not starters, just make sure you treat them all as you would want your son treated. Give them respect, encouragement, and treat their personal goals as important.