It's worth noting that when you first install it, steam asks to install a service to assist with its duties, presumably for most install tasks. Steam has been around long enough and that service is now trouble free that it became part of the furniture most ignore as part of the background. That's aside from how users may be trained to hit 'yes' on any permission box that comes up to swat it away and play the game.

> It's worth noting that when you first install it, steam asks to install a service to assist with its duties, presumably for most install tasks.

They do this because Steam was originally designed in the XP era when you could write whatever you want to Program Files without escalating to admin, and instead of refactoring where they put their files when Vista made the permissions more strict they started installing that backdoor service which lets them keep putting everything in Program Files without triggering UAC prompts all the time. It's a pretty gross and unnecessary hack, but I doubt they're ever going to fix it at this point.

I don't think this is why -- Steam actually sets permissions on its subdirectory so that any user can write to it. (This means that while installing mods, for example, I can write to that directory without having to deal with UAC/sudo.)

Although I'm not fully linux knowledgeable, I think they put everything under the user profile in ~/.local/share/Steam for similar reasons so they can do software installs with no elevations. They're not the only ones taking that approach though, it's become common across OSes to offer an easy/quick installer that dumps itself in your user profile because that's seems to matter most to getting users up and running.