Worldbuilding for yourself: Why do people do it?

It seems like a lot of you guys are doing the life simulation type worldbuilding where you imagine yourself as the main character of the world you're working with, exploring the environment, meeting and befriending the inhabitants, and living a life there. I'm talking about the stuff where you picture yourself walking through the world you're building, noticing all the little details about the buildings and plants and animals and all that, think about what you're doing in the day, what tools you're working with, what foods you're eating, all that jazz. I know I do this a lot, and I'm just curious as to why people do this, what it does for you guys, whether it actually helps with the process of creating this world, and all that. I think I do it because I find building the world more fun than building the story, and I get to do all the little personal details that I might not be able to include in a story, but I can still use it as reference if I need to. So yeah, just wanted to know what the rest of you think, and see if there's anything I can learn from you guys when it comes to all this. Thanks!