Have you looked at your homedir lately? Cluttered with dotfiles, isn't it? If you don't know what a 'dotfile' is, look at your home files with
ls ~/... now look again with
ls -a ~/. Quite a difference, right? In theory we have some modern XDG standards that will take a lot of that clutter and put them in
~/.cachebut that requires the programs to adhere to the XDG spec. Since we're in The Year Of The Linux Desktop we're actually in an exciting time where we are seeing a lot of developers making software (including games!) for Linux without actually being in the ecosystem from the start. So a lot of them aren't necessarily using Linux day-to-day. They aren't aware of how your homedir can get littered with crap from software that doesn't understand that
~/is not the same as "My Documents" on other operating systems.