Comment by brookst

That’s why head units stay in low power mode for 30ish minutes when you turn off the car.

They do not stay in low power for weeks. Car batteries are really not that big, and cranking an engine takes some amps. I had a Subaru crosstrek that was recalled because their cellular modem was drawing IIRC 10ma 24/7, which would kill the car if it sat 3 or 4 days.