I'm guessing it starts as a habit, they either weren't taught in driving class or it wasn't enforced, then it became ingrained and they never got curious about what they could be wrong about,or what it means that their car rocks when they step out.

Even with a "car guy" who was working on my rear wheels (fwd) he asked if I had AWD. No buddy, I just remembered to set the brake before you got it up on the jack.

For curious readers, if you always park on level ground, just set the brake anyway as a drill. If it's busted, you'll get a chance to fix it before you need it

I also always turn my headlights on. It uses a little more gas but saves the judgement call of wondering whether it's real dark enough or whether the computer will turn them on for me. Always on.