system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why every car I've driven only has the defrost option set to "defrost the windshield" or "defrost the windshield and blow on feet."

I get up really early for work so I was super cold the other day...anyways, I noticed you can't really warm your hands and defrost the window at the same time. You have two options, you can just defrost the windshield or defrost the windshield and blow air on your feet.
gpt
Heating the window is, of course, a safety feature.

As for the "warm feet", that's just blowing it at the bottom because warm air will rise, so it makes the most sense to send it out at your feet.

You might look for an aftermarket accessory called "gloves".