"Hair bands" was the derogatory term popularized by MTV in the 1990s and derives from the tendency among such bands to have styled their long hair".
The true title these bands went by during the 80's was GLAM Metal..
Grunge hit the mainstream in the 90's and wanted to be separate from the 80's bands thus giving them their own identity not associated with "Hair Bands" or Hair farmers..
Van Halen was lumped into the Hair band title because they came from California and were apart of the sunset strip era where most of the hair bands originated from..
Keep in mind the band "Angel" because they were before Van Halen and were as much apart of the Glam Metal scene.
So basically.. You can create a list of bands during the 70's and 80's and call them a "Hair Band" But the term was thought up and as above was a derogatory term used by the wave of Grunge fans..