Well, most of my lower-bitrate tracks are non-LAME MP3s dating back to the beginning of the decade (or lossy-lossy transcodes from before I knew any better), so the encoding quality wasn't all that great to begin with.
That's also why I added the "generally" qualifier to the very beginning of that sentence, and emphasized "occasionally" later. This is particular to
my music library, and may not match others' experience.
And like I said, that's pretty much only because I'm using a setup that tends to bring out just about every imperfection in the track - distortion, missing or weak treble/bass, etc. On regular headphones, only the very low-end of the encoding spectrum makes itself apparent. (And, yes, I do have a small collection of those tracks, too, for which I can't find the original source to do a better encode.)