Because they’re 2 different types of vehicle
You’re inside the moving vehicle and should you not be attached to it you’ll bounce around the inside or go flying out the window in a crash
A motorcyclist is not contained, and thus it’s dumb to attach them to the dangerous and heavy metal should a crash occur. We instead require protective gear (unless you live in a shitty state) so you get less injured if you go flying
My parents both openly smoked weed in front of my from a young age. I was told that as long as I was home by curfew and didn’t come home in a cop car they were fine with me doing basically whatever cuz they knew I wasn’t a complete moron (my dad worked in the school system and knew all the ACTUAL problem children really well, they hated me because of that so I never got to be a hoodlum lol), though my nugs WERE taken from me at 15 because “you were dumb enough to let us catch you with it” which is fair but I say they were out and bumming off of me without saying so lol
As for sex I got a quick talk about using a condom after my dad caught my GF and I doing it, but otherwise it was left mostly unsaid cuz my sex Ed wasnt trash