The exact mechanics of his decision are left vague and unclear, and a lot of people want to know exactly how this works.
It seems more plausible that Steve would instead be in an alternate reality, living a more heroic, Captain America-ish life with Peggy.
The following post contains SPOILERS for Avengers: Endgame, or maybe it doesn’t because even the people who made the movie don’t agree on exactly what happened at the end.
Personally I can’t wrap my brain around Steve Rogers living in his own past for decades.