Why are so many albums poorly remastered onto cd

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.

Don't tell me I'm in the minority in thinking that most remastered CDs I listen to are actually done pretty well, often better than ever before.

Mapman,
For me it is a mixed bag. Some are great, others mediocre.

Mapman,

I generally find classical reissues to have good sound, often better than the original vinyl issue (e.g., DG recordings from the 1970s). A lot of jazz reissues sound good too. For me, much of the pop/rock catalogue sounds quite bad in recent reissues. I think it is a deliberate--trying to match the loudness of current recordings via heavy use of compression.

"I think it is a deliberate--trying to match the loudness of current recordings via heavy use of compression"

No doubt many more recent remasters seem to do this compared to earlier CD versions.

I do not have a problem with increased loudness categorically. It all depends on the details of how it is achieved. Many early CDs did not make use of full dynamic range available in CD format well. Many newer remasters do. Its when waveforms are clipped in the recording that worse sound is inherent. Increased loudness does not always mean clipped waveforms, though it is most common in pop music these days similar to how popular music on 45s back in the day were never a popular format in regards to sound quality.