Every few years I get the customization bug and trick out my desktop. Then things start breaking down slowly. Then I get frustrated and reinstall vanilla gnome, swear off customization forever, and feel better.

For gaming its Plasma.

Knowing the default DE’s idiosyncrasies also helps with work – I’m never surprised when I reinstall/install a new machine. Same goes for aliases. No for me, knowing the commands themselves, however cumbersome or verbose, helps me better deal with freshly installed machines.