Many car cassette players had a search function. They would detect the momentary silence in between songs when you hit fast forward or rewind and would stop at the exact beginning of a song. My last cassette player, before I replaced it with a CD player, did this.
Not in the 70s, but various manufacturers made phonographs for use in cars in the 50s and 60s. RCA made an under-dash automatic record changer for use in automobiles in 1961. It could play up to 14 45-RPM records and was supposedly skip-proof, too.
There was a cost. The play head did not disengage during FF/REW. Both the head and the tape suffered additional wear during seek operations - and if the tape stuck to the capstan wheel during FF, your cassette was ruined.
Si
That’s mostly why I replaced it. I was playing my iPod through the stereo using one of those cassette adapters and the sound started to be really off. It sounded like the tape heads got misaligned and was only playing through the speakers on one side. I replaced it with a stereo with an aux jack on the front of it.
Tapes cost less when they weren’t holding music. Cassettes were the cheapest medium you could buy software / computer games on. I’m not sure what made floppy disks more expensive.
A CD still typically costs a bit more than vinyl.