Of course it's possible - but not very likely - the point for artists (and particularly the label!) is to improve on what they did before. For the label the rationale is to ensure that fans get something different from what they already own so that they actually want to buy it in the first place.
There's also the (very good) possibility that the original mastered copies do not exist any longer ( record labels back then often thought of records having a very limited life and often couldn't be arsed in archiving them properly/fully.
I agree it's annoying when you listen to something you know well only to find it doesn't have the same edge after its been remastered. Labels and Artists often forget that the magic that happens on a record is literally that; magic. That tampering with something which already has perfection doesn't make it an more perfect but in fact often makes it less perfect than it was originally.