Because they're i) mechanical and often need to be repaired and ii) shit. Seriously, tape is fucking awful for all use cases except "no other formats exist at this point in time", and that was true in 1982, but not today.
Tapes were pretty durable. Degraded tapes at least played, unlike scratched CDs which could be be effectively ruined pretty easily. Plus portable tape players could be jostled around during playback with effecting anything, while cheap portable CD players would cut out.
I use the tape deck in my car more than the CD player, and almost as much as I use the radio.
Granted, that's mostly because I have one of those tape-to-3.5mm adapters, but even the actual tapes I pop in every once in awhile are more convenient than CDs, not to mention more space-efficient.
