As I understand, flying gliders without a chute is quite common in the
USA. I'll never understand this.

Me neither, but this time the folks in the glider weren't the ones that
needed a personal parachute.

I know, but it was close.

BTW, some may argue that passengers wouldn't jump anyway. This has been
proven wrong. One ore two years ago, there was a successfull bail out by
a passenger after a mid-air in Switzerland. The passenger was 80 years
old and it was his first flight...