In many ways, especially the US, the idea to 'do it yourself' can often come up as being illegal and even stand you in a way to get your property seized or at least your buildilng on hold. By making 'laws' that say this and that about how a building HAS to be build etc, most people can't build their own structure and also be following the rules.

I have built my own little tiny house however, and really enjoyed it, but it was a challenge with permissions sometimes. :)