Each individual patch bring a batch of new content. The most chunky patches would offer new raids and/or dungeons, which, like it or not, sadly seems to be the only thing most mmos manage to create to keep their player base engaged once they hit the level cap.
A lot of people, when they start playing on a private WoW server, want to progress alongside the community, through each individual patch. They want to get their Tier 1 set, then progress through Blackwing's Lair and grab their Tier 2, and so on. From what I've read, no private server has ever properly scripted Ahn'Qiraj 20-40 in a satisfactory manner, let alone Naxxramas, but that doesn't seem to make the playerbase lose hope.
Nobody wants to go back to Molten Core/Blackwing Lair once their guild can competently farm Ahn Qiraj, so obviously the people who didn't get the chance to enjoy the sheer pleasure of the tank and spank encounters you'd find in most of Molten Core/Blackwing's Lair wouldn't want to join a server who's population is so far gone into late-game content.
As for the fishing shit, I don't know, it might just be Elysium is a shit server.
Further ranting on why some people might prefer old-nost versus the new elysium servers:
Once you hit level 60, there isn't really that much to do pre patch 1.7, at least in my opinion. Running level 60 dungeons to gear up and get your pre-raid best in slots is well and good, and you might (or might not) have fun doing some world-pvp or just enjoy Vanilla's strong player interactivity, but the truth of the matter is that unless you're autistic enough to grind rank 13, you'll eventually end up raid-logging (i.e. logging in just during raid nights). For a lot of people, Elysium isn't their first time dabbling through Vanilla, and exploring Stranglethorn and having their share of world pvp, while exciting, won't hold enough charm as it did the first 5 times they leveled up to 60.
That having been said, a lot of people might be new to Vanilla, so of course they'd want to start on fresh servers where most people aren't even 60 yet, let alone well geared.