Along with looking really cool, I think there were some other benefits as well.

Having a self contained case, and a pretty small size that can easily fit in your palm was pretty practical. We’d go on road trips and it was nice to be able to eject a cartridge and just put it on the dash or whatever.

Same as with a tape, making a recording was sort of time consuming because you couldn’t just drop files and burn to disk). Unlike a playlist that has infinite capacity, when recording to disk you had limited capacity so needed to make more careful editorial choices in your mix.

It was really nice giving or receiving a mix that a friend had taken the time to make :)