There are already, and Epic has acquired multiple companies in that segment. https://www.gamesindustry.biz/articles/2019-11-12-epic-acquires-megascans-creator-

There are already, and Epic has acquired multiple companies in that segment. https://www.gamesindustry.biz/articles/2019-11-12-epic-acquires-megascans-creator-quixel https://www.gamesindustry.biz/articles/2019-11-12-epic-acqui... Edit: well not of entire cities, more about 3D assets. The city itself was built procedurally using Houdini.