It straps you to the seat so when the plane suddenly drops 50 feet due to turbulence your dumbass doesn’t launch into the ceiling.

Yeah, and this is a much more frequent thing than crashes. I’ve been on planes multiple times when there was sudden turbulence and people without seatbelts lifted out of their seats. I don’t think any of my personal experiences resulted in someone hitting their head, but that happens. There was just video of one earlier this year.