People are aware that they must remain throughout a Marvel movie because they know they must. There will almost always be two post-credits sequences, not just one.

These post-credits scenes are significant because they provide a preview of what will happen next and hint at a possible sequel. Guardians of the Galaxy Vol. 3‘s official running time is 2 hours and 30 minutes, which already includes the mid- and post-credits scenes.
What happened in the mid-credits sequence and post-credits scene in Guardians of the Galaxy Vol. 3 then? Can we anticipate a new Guardians film?
The new Guardians of the Galaxy are gathered in the scene towards the middle of the credits. They include Blurp, the fuzzy alien, Rocket, Groot, Kraglin, Phyla-Vell (a young woman spared from the High Evolutionary), Cosmo the Spacedog, and a transformed Adam Warlock.
The new squad is tasked with saving a planet in the scene. The Zune Peter had given Rocket (now Captain Rocket) was in his hands. The new Guardians are then questioned about their favorite musicians.
According to Phyla-Vell, she likes Korn and Britney Spears. Garth Brooks is Kraglin’s selection. The Carpenters, according to Cosmo, “don’t have a single bad song,” whereas Adam Warlock chooses King Crimson.
Rocket wakes up Groot, who suddenly appears larger, as their adversaries get near. The new Guardians of the Galaxy then engage in combat while Redbone’s “Come and Get Your Love” is playing in the background.
Peter and his grandfather are shown enjoying breakfast together in the post-credits sequence, and Peter is heard discussing what he plans to do with his life now that he is no longer a superhero.
They discuss how Peter works mowing the lawns of his neighbors and how Peter’s step-brother, who isn’t shown in the movie, isn’t doing his share. The closing title card that reads “The Legendary Star-Lord Will Return” then flashes across the screen.
The third installment of the Guardians of the Galaxy franchise, directed by James Gunn, will be the final. He recently stated on Twitter that he “always meant for the story to stop with Vol. 3”.
Additionally, after the third Guardians movie, performers who played the original Guardians of the Galaxy members like Dave Bautista and Zoe Saldana indicated they were done playing such roles.
Even if the original cast (with the exception of Rocket and Groot) would no longer be present, there may yet be another Guardians film with a fresh crew in place. Additionally, the post-credits sequence implies that Star-Lord may star in a solo movie or continue to feature in subsequent Marvel productions.
There have not yet been any announcements. But at least we know that in Guardians of the Galaxy Vol. 3 the Guardians go on and find the tranquility they merit.