One of the rule changes proposed to the NFL was allowing coaches to challenge any play other than scoring and turnovers (which are already automatically reviews by officials), and this proposal was rejected.
There is absolutely no reason what so ever for the NFL to reject this proposal. As long as coaches continued to be limited to two challenges, this in no way threatens the flow of the game.
Instant replay gives referees an opportunity to get every call right. Nobody wants to see a game decided by the referees, and instant replay can ensure that the players are the ones deciding the outcome.
Some of the most signifying plays in games are currently not allowed to be challenged by coaches, none more obvious than pass interference. Pass interference calls can legitimately be the difference in a football game. It is a penalty that can amount to any kind of yardage and put teams on the one yard line. Pass interference is also one of the more difficult calls for referees to make. The penalty has become so ticky tack, and during a full speed game, it is unrealistic to expect the referees to get the call right every time.
There are also specific rules as to what is or is not pass interference, and for that reason, it can always be correctly determined through replay.
With the technology at their disposal, it is ridiculous that the NFL is limiting the use of instant replay. The game could only get better by ensuring that every single call is correct, and too often teams find themselves suffering tremendously because the referee missed a call.
Referees cannot be expected to get every single call right. No one is perfect, and they will all at some point make a mistake. There’s no reason the NFL should pass up on the opportunity to ensure these mistakes can be fixed, having no impact on the outcome, which should stay in the hands of the players.