Classic servers are a peculiar thing. They exist to bring back the past — a past that for many people, in many games, is often highly preferred over the existing state of the game.
Some of the more notable classic servers are EverQuest’s Project 1999, Star Wars Galaxies Emu, UO Second Age, and DAOC Uthgarde. What they all have in common, unfortunately, is a third party operates them because the developers either ignore the idea or refuse to provide the service.
Let me first disclaim that I do not endorse the act of emulating servers when done illegaly, and I do not encourage piracy. I have, however, tried them all and find them to be better versions than the real and official run/supported game becuase they exist for one reason: Giving players the opportunity to play once again when the games were at their best.
I wish developers would officially support vanilla/classic servers if enough players want them. These servers require very little updating, and would bring more players back to play. Many players wanting to play on classic servers are also fine with paying a subscription fee which means even more money for developers.
Classic servers seem like a win-win. Developers get more money (that can be used to develop the game for the other customers) and more people talking about and playing their games, and the players get the games they want. Heck, even games with a dieing population could be completely turned around by simply offering a classic server. The pros outweigh the cons for many games out there.