myDeaconmyhand
First man to get a team of horses up Bear Mountain
You also don't want to start each movie or episode with a list of excuses why certain characters are indisposed. That would get old quickly.
True, that's why they should pare down the plot and scope of each film to fit the starring character, so the question of "why isn't the hulk/Thor/Ironman here to destroy this ship/blow up this dam/pick up this school bus" never comes up.