I stay until the lights come on and the kids cleaning up make me leave. Dad & I went to movies all the time when I was a kid, and he hated dealing with the traffic jam in the parking lot.
Marvel is known for "after scenes" but they didn't start it. Mel Brooks is notorious for scenes after the credits. You never know what you may see. Even in the credits.
But then, there was the 16 minutes of credits on one of the Harry Potter films - intolerable.