Mark Millar says the bulk of D.C. roster is not "Cinematic".

He beat up the trucker in the diner because the trucker was a bully and needed to be taught a lesson. Unlike the Avengers, Superman and the rest of the JL help the ordinary people that the Avengers consider too unimportant or too poor to afford the Avengers' "pay grade". Superman stops robbers, Barry Allen stops a armed robber in a grocery store, those are things the Avengers refuse to do because the ordinary people can't afford to pay the Avengers' "pay grade".

The Avengers need to be paid a substantial fee for their services since they don't have regular jobs like the JL do. Steve Rogers, Bruce Banner, Natasha Romanov, Clint Barton, Wanda Maximoff don't have regular jobs like Clark Kent, Diana Prince, and Barry Allen do. That's why the people need to meet a certain income/wealth level before the Avengers will help them because the Avengers need to make sure that they get paid for their services.

Agreed. Superman is the most powerful person on Earth, but he doesn't want to rule over the Earth like Captain America does and instead respects the authority of the people and is willing to answer to the people. That's why he willingly surrendered himself to the military even though they had no power to force him to and why he appeared before a Congressional hearing when summoned even though Congress had no power to make him appear. Unlike Steve Rogers (who spit on the Constitution that he swore an oath to defend and betrayed the country that gave him his superpowers by giving him a super-PED even though he was too lzay to exercise and train like the other soldiers and who aids and abets a double-murderer to flee from the police) and Natasha Romanov (who told Congress that they can't arrest her because she's an Avenger and the Avengers are more powerful than the people so the Avengers are above the people's laws and don't have to respect the authority of the people or answer to the people for their crimes.