If you login as a blank account, for example if you want to mod something and test it out with something like eclipse, it will have a 0 for the access code, but when you go back to the launcher it asks you to log back in, this has never happened in older versions though. (I have keep me logged in too)
Please Note this does not happen 100% of the time, its more of a 50/50 Chance + how long you haven't been on minecraft or you use a launcher like lunar or badlion.
Hi Tyler, we changed how we handle access tokens in early December. It could be that third-party launchers are not conforming to the new format, which causes you to have to log in again if you switch between launchers. Please consider only using Minecraft Launcher, and report this with the third-party launcher developers.