Yes, there are some reissues that suffer from tapes deteriorating over time, and a whole lot more reissues and new issues that suffer from shoddy and indifferent mastering/production.
But, I would guess that the primary driver for the pervasiveness of bad sounding recordings is public demand--"we" want compressed music to listen in high noise environments (car, subway, airplane, etc), "we" have become accustomed to, and prefer MP3 sound (a blind study showed that most young listeners prefer MP3 to CD).
Of course, by "we" I don't mean those of us who are concerned about sound quality, but, that "we" are in the minority. Perhaps, some day, those same listeners who don't care about sound quality will come around, and in that case, the recording industry will be more than happy to resell their catalogue in a higher quality format. In other words, the industry will make more money by selling crap recordings, as well as more expensive "audiophile" recordings, than it would make by making all issues decent in sound quality.
But, I would guess that the primary driver for the pervasiveness of bad sounding recordings is public demand--"we" want compressed music to listen in high noise environments (car, subway, airplane, etc), "we" have become accustomed to, and prefer MP3 sound (a blind study showed that most young listeners prefer MP3 to CD).
Of course, by "we" I don't mean those of us who are concerned about sound quality, but, that "we" are in the minority. Perhaps, some day, those same listeners who don't care about sound quality will come around, and in that case, the recording industry will be more than happy to resell their catalogue in a higher quality format. In other words, the industry will make more money by selling crap recordings, as well as more expensive "audiophile" recordings, than it would make by making all issues decent in sound quality.