What were music videos made for in the 70's?

Yes, Top of The Pops was the place to see pop videos but they were nearly always truncated.
In 1975-76, as a student I used to go to a club at lunchtime, near the university campus, where they had a DJ, bikini girl dancers and the occasional pop promo film projected onto the wall.
I also remember seeing video jukeboxes in pubs.

 

seems like some of them were made for about $25

 

Just why this is considered by many to be the first music video remains a mystery to me.

 

Music Videos would also be shown before Movies/films in the theater along with the trailers for upcoming and between double features.

 

Aside from Top of the Pops Whistle Test showed promos including Genesis I Know What I Like, Steely Dan Reelin’ in the Years. Also Tiswas showed all sorts of stuff including Zeppelin’s Black Dog from TSRTS and The Stranglers Five Minutes and it’s B side Rok It To the Moon. I recall Bad Company made a film for Good Loving Gone Bad that TOTP showed. Bowie’s John I’m Only Dancing was another one on TOTP.