I would have to say that headphones are just a bit more popular than ice chewing.
I kid you not.
You can still do transcriptions by ear and analyze performances even with a pretty low-end audio playback system. Music is primarily about the relationships of sounds (and not sounds) over time and across frequencies, so most of these things are preserved. It's about X compared to Y, how much of Z, and so on. If both X and Y sound fuzzy and a little lean on bass because of the poor playback system, you can still tell what the difference was. Most (not all) musical details are "big" enough or are of the nature that they are not lost in the noise of a bad recording or coming out of an iBud; also, the more subtle something is, the less likely it needs to be precisely the way it is, as an overgeneralization.
It's not like the rhythm or pitch of some notes are going to change, just because the sound system sucks.