alt Hacker NewsA big driver of cassettes then was the write ability, unlike 8 tracks. You could borrow your friend's new vinyl album, pop in a new cassette tape on your hi-fi, and record a copy of the album to the tape. Of course the Walkman then made listening to your new album fully portable.
There were consumer 8-track writers, and you could buy blank 8-tracks. But it was more expensive and less common; just never caught on.