I believe it was just to deny them performance royalties, an issue that initially flared up specifically over Diary of a Madman crediting Rudy and Tommy as the rhythm section. Their songwriting credits remained in place.
The 2002 remasters is also when The Ultimate Sin, Just Say Ozzy and Live & Loud were pulled out of print. Why? They all feature "Shot in the Dark," which had been the subject of another lawsuit. Phil Soussan co-wrote the song with his previous band and brought it with him when he joined Ozzy's band. Ozzy got a co-writing credit with Soussan and the song became a massive hit for Ozzy and the previous band was now thinking "what the fuck?" So inevitably, every album that featured the song was straight-up pulled out of circulation in 2002, except for the Ozzman Cometh which just swapped it for Miracle Man (but now The Ozzman Cometh has itself been pulled out of print over the song "Back on Earth," which was Ozzy's one proper solo single/video between Ozzmosis and Down to Earth). The song only came back to Ozzy's live set in 2010 and after that it remained a staple on all of his tours, just as it had been from 86-92.
And of course, it would be remiss to mention the 2002 remixing of Bark at the Moon, which unlike the other 2002 mistakes remains unrectified. Blizzard and Diary have been restored, Ultimate Sin and the two live albums are back in circulation, but the original version of Bark at the Moon has been done away with for over 20 years.