Would you be any happier if you were sitting in your airplane waiting to depart only to learn that you couldn't depart because your flight crew was stuck in a long security line?

If the crews had to show up earlier at the airport then that time can not be counted as part of their FAA required rest periods. That means more crews would be needed to allow for the longer layovers and each crew could fly fewer flights during their allowable duty day. The result is less productivity from the crews and higher costs for the airlines. That certainly won't help the passengers any, either.

Typically the crews must be at the airport either 45 or 60 minutes prior to departure for a domestic flight and about 90 minutes prior for an international flight. They have to get through security fast enough that they'll still have time to do their preflight duties and be ready to go at departure time.