Is this a joke?

The people who don't wear seatbelts are in my observation old folks who grew up without them or before using them was mandatory. It's just their habit.

I've almost never seen a person under about age 40 not using a seatbelt.

No. I don't know a lot of people that don't wear seatbelts, but they all smoke weed. All of my friends that died in car wrecks weren't wearing seat belts and would have definitely tested positive for THC.

I don't know any old people that don't wear seatbelts.

The people I do know that don't wear seatbelts also live pretty otherwise high risk lives, drug dealers, strippers, street gang members,etc.

While I do not commonly ride in cars driven by people outside my family, my experience has been quite the opposite: when I do ride in cars with older people, they buckle up as a matter of course, while when I ride with younger people, they are much more likely not to.