Because VRChat is not very stable and crashes will still happens. Which means you must do it over again or lose game progress with friends if you crash in the middle of the game. Especially long RPG worlds need feature to store game data in special cache file, so you don't worry if you have crash and can join again to last remembered spot in the world.

Some online games have this feature, so why not in VRChat? Crashes are no fun and it sucks big balls, because you don't want spend again hours do it again.

Can it stored in the cache file? This cache file can also have limited time before it's invalid and will erased (log back inside 10 minutes for example). But it should nice if it stays there and if you log back in world, you get question to restore the game progress or start over again. If you want continue with progress, it will load again and you're teleported to last stored position.