Well for vBulletin specifically it's that the software was bought out by a company called Internet Brands, who got rid of the original team and screwed up the last three versions of it.
vBulletin 4 is okay, but 5 and 6 are poorly coded, extremely inefficient and full of bugs even today.
Some of the original team went off to create XenForo, which has basically replaced vBulletin for most large forums now, though that itself has its own issues.
vBulletin 4 is okay, but 5 and 6 are poorly coded, extremely inefficient and full of bugs even today.
Some of the original team went off to create XenForo, which has basically replaced vBulletin for most large forums now, though that itself has its own issues.