Because Mojang has told them that they don't know how to build games. (Source: I know people that work at Lego and met him in person) In general, many people p

Because Mojang has told them that they don't know how to build games. (Source: I know people that work at Lego and met him in person) In general, many people prefer simple games with simple rules which they can use to build more complex systems. The reward is the appreciation of ingenuity in the application of one's imagination with the limited resources provided in the 'physical' environment (in the virtual world). When the users are not allowed to express their ideas without mental restrictions or simply being forced to think about abiding by the rules of censorship, the imagination is being confined within artificial limits and this removes the joy of the free and innocent exploration of possibilities. Lego enforces many rules about the play experience that hinder the creativity compared to the freedom you have in Minecraft. This is exactly what the OP has pointed out as well. There's also something about the size of the company that tends to bring an unnecessary overhead and sluggishness into an otherwise lightweight gaming experience. The phrase "the slower it is, the more enterprise it is" is very often true in the corporate environment. As the OP writes the moderation costs were one of the biggest expenses for the Lego Universe project. This was essentially the 'Lego Minecraft'. People loved it, but the company pulled the plug because they couldn't make enough money out of it which is their primary goal. They also wouldn't allow the fans to run their own servers or to create mods for the game (AFAIK). There is now already a Lego theme featuring Minecraft which was released after the company realized that they've missed out big time on not buying the rights for it while it was getting popular.