Addressing some points here...
1. It does open doors for a lifetime. Especially in baseball itself. Even if it's doing $80 an hour lessons at the local academy. Not bad money by the way. Former minor leaguers never had it better with this personal instruction obsession we now have.
2. The 'value' of these players is highly debatable. As someone mentioned most of them are there to play catch with real prospects. Every once in a while one of them fools you and makes it - good for them! The ones the club really wants got bonuses to help them through these years. And the lower level minor leaguers are very replaceable. By the time you get to that point you are separating kids by hairs, very small degrees if talent and mostly a guessing game. Like which 86mph guy does the D1 take to round out their bullpen. Very replaceable.
3. Fair... what does that even mean? I hate to be so cliche but life is not fair. I wish my kid was more fast twitch. It's not 'fair' that he's not. I wish he was more recruitable in baseball than he is in football. But let me ask you this... if he gets a football scholarship some day, that same scholarship thousands of football kids across the country were hoping for is it 'fair' to those kids left behind if he does nothing but complain about the fact he got a football scholarship rather than a baseball scholarship??
Bottom line be thankful AND HUMBLE about the opportunity you have been given. Appreciate it. Work hard mostly for yourself and your future family but maybe a little for those kids left behind too. Honor the game. That's what I would tell my son if he were drafted in the 40th round with a bonus of a bus ticket or if he takes a scholarship to play football. Be grateful and humble and like Capt. John Miller said on the bridge - EARN THIS!!