This is the greatest advantage an official release has - these servers and characters are going nowhere.
Many people do not want to dump hours into a character only to find the server has been taken down the next day. You certainly could - although, as we saw in Classic, official Blizzard servers really drove a stake through the heart of a lot of private servers. Not everybody could do everything in TBC - in a dungeon with no crowd control? Tough, you'd better hope you can kill everything fast enough! At the time, the game was much more of an RPG, including having to complete extensive quest chains and multiple dungeons to even access the raid content the game had, far more emphasis on crafting your own great gear, and a much greater sense of unique class identity. Just like Classic WoW, Classic TBC will offer players the chance to see what the game was like back in 2007 - long before many systems were either implemented or removed from the game to streamline the playing process as much as possible. Why would I want to play this old version of WoW? Anyone with an active WoW subscription can access this version of the game on existing Classic servers as they roll over to TBC some time in the coming months. At Blizzconline 2021, Blizzard announced that they would, as expected, be launching a classic version of The Burning Crusade - the first ever World of Warcraft expansion, and a fan favourite.