That was more my 3.5 and 4e experience, it has not been my 5e experience. A GM ran Curse of Strahd, we made PCs for it, retired them at the end of the module, then switched GMs and game systems. When the pandemic started, I made an online group, and I ran Dragonheist. PCs were made for the module and while I carried the campaign a little past the end of the adventure, they then retired and we rotated GMs and started again with Descent into Avernus. I've run Light of Xaryxis twice but both times were standalone and PCs retired at the end.
Campaigns have been pitched as either "I want to run X adventure" or "I want to GM X system", but generally start with someone offering to GM and picking the module they want to run and the players then building for that module.
That's my two current groups, a GM wanted to run Rime of the Frostmaiden, so I made a PC for it and expect them to retire at the end, and I wanted to try Daggerheart, so I pitched a one-shot that went so well that it's become a full campaign.