The perception is legacy
When CD's first appeared they were fairly hideous, plastic sounding things that illustrated the weaknesses of the low resolution, my first CD player had an 8-Bit DAC in it to exaggerate the problem.
Then in the 90's CD players started using bitstream which was basically oversampling or anti-aliasing and their sound quality was transformed. That said the vinyl purists had already made their mind up and and advancing technology wasn't going to change that.
When MP3's appeared they were generally quite low bit-rate, 128k was the norm, maybe 160 if you were lucky. They did all kinds of odd things to the sound, a highly compressed pop track sounded fairly normal but an orchestra sounded like a Casio keyboard. FLAC was preferable as it retained the CD quality. MP3's improved as the bitrate went up, now usually 320k and you can't tell the difference, however the FLAC purists are the new vinyl-types and have already reached their conclusions.
It's a pity that we're still using MP3, MP4 has much better compression enabling decent HD audio with sensible file sizes, there are few devices around these days that don't have sufficient CPU power to play them.