CDs skip very easily so they're not good for portability. So that limits their use to in the house, and they're you're competing with vinyl. Cassette fill a niche in the nostalgia world being something you can more easily use on the go.

There were many portable CD players with enough buffering that they'd never skip. Panasonic Shockwave (IIRC) for example. And car heatunits.

You had to get a very old or seriously cheap portable player to get skipping.

Cassettes get distorted too when moving (.e.g running). There’s very cool tech in some models that prevent this distortion but they are more expensive.

I had lots of CD and mp3-CD players with good anti-skip. Some would even buffer enough or the song to stop the CD for several seconds at a time, especially so on my later mp3/ATRAC CD players. The crappier ones added crappy audio compression to fit it's tiny memory, but better ones could do the raw data and had no (at least to me) loss in quality and later the mp3/ATRAC ones would just buffer the actual file data.

I don't think I've ever experienced a car CD player skipping due to shock. I'm sure it could happen, but I don't do much trail driving at high speeds personally.

I listened to my CD players while biking, hiking, and more. No reason to leave the CDs at home unless you already upgraded to one of those fancy hard drive mp3 players.