The way internet sites go that's probably because the owners of the sites shut them down. The vast majority of internet sites are run by individuals and in time they tire of them and decide they are too much trouble or expense to maintain and just abandon them. A personal website that makes it to 2-3 years old is quite old by internet standards and most don't make it past one year. Businesses are really very similar most being started by an individual and failing by the end of the first or at most second year.
No one has taken any interest in this forum since someone many years ago asked for it. Moderators appointed to it have never stayed long enough or been active enough to keep it going but I leave it for those who have some interest in the subject even tho it hardly ever has an active moderator.
I've updated it and added some comments. If anyone here actually has enough interest in the subject to do a bit of work that first link would be a good one to use to add some more links to this thread.