1. Back in 1979 there was no self-serve. You had to wait for some gas monkey to come gas you up. and ...
2. There are many more gas stations now than 25 years ago. If one doesn't have gas, the fellow a block from you will.
Try studying economics again. The law of supply and demand does not rest upon the identity of the person filling the tank. If prices are capped, supply will shrink. Regardless of how many stations there are or if you have to pump it yourself.
SD