Minecraft's developers have explained why the Ender Dragon is bound to its own realm underground and not allowed to roam the overworld.
For a game about building and creation, Minecraft sure has a lot of ways to absolutely ruin all of your creations, and the progress you made towards accruing the materials for said creations. The developers at Mojang seem to understand that, with the CCO of Mojang Jens Bergensten admitting that they probably would not add the Creeper to the game today, despite being the series de-facto mascot, since the ability to destroy builds would undoubtedly be controversial if implemented 14 years later.
In a video titled "THE BIOME THAT BROKE MINECRAFT" Bergensten and creative lead Cory Scheviak talk about designing difficulty in the iconic survival game. "We have this guiding principle that bad things happen, but they're technically the player's fault" Bergensten explains, saying that every issue a player should face is either caused by them or something they could prevent (like stepping on a rogue pressure plate), with the aforementioned Creeper being an exception.
Another one of the rules set out in the video is "don't add features that wrecks player's builds." Scheviak says that "it wouldn't really be a good idea to bring the Ender Dragon to the Overworld because," pausing for a ton of different reasons (such as "I don't need that kind of stress," "it destroys everything," and "it might break a wing on an ice spike").
He adds: "You're just home planting your potatoes and suddenly there's a dragon coming after you." Bergensten agrees: "That's not a great game experience."
Bergensten explains that "players have a different appetite for challenge and difficulty," so a boss fight that comes flying at you and destroys everything isn't exactly going to suit everyone. He cites the Wither boss as an example, which has destructive power akin to a dragon, but you choose when and where you'll summon it for a scrap, allowing you to minimise damage to your house.
