The NFL is a copy cat league and no one sits QBs drafted in the first 10 picks.
There's always a risk of injury in football. It's inherent in the game. You play Tom Brady when you have him. You don't sit him because it's raining, your center has the shits, or Ray Lewis is on the other side of the ball. You just don't.
Even if you are a bad team, you play the guys who give you the best chance to win that week. Jobs are on the line. If the Patriots have a 1 win season you could very well see Mayo and crew getting fired.
These are also pro athletes. They are wired to play. The only way for Maye and the Patriots offense to improve is to get reps. And if Maye isn't the guy it is better to know that now than 3 years from now.
You can't convince me that guys who have flamed out like Wilson, Darnold, Fields, and Jones would have benefitted from a year on the bench. They all sucked for somewhat different reasons and got exposed for it in the league. It happens.
Drake Maye is going to start Game 1 and every game this season and next. He may be great. He may suck. But his window is now.
And if you're Kraft, you don't go into this season expecting to make the playoffs. What you hope for is they play some competitive games and win a little. But more than that, you hope the fanbase gets excited about the future because of what they see on the field and not who is on the bench, who they can sign in free agency, or who they can draft.