Why aren't there more earthships?

  It’s also difficult to get most counties or cities to grant you a building permit for a house that uses old car tires and rammed-earth construction. Earthships tend to be relegated to communities that have worked out deals with local governments. Deals can take years to obtain. Building without permits happens too – but always at the risk of being fined and torn down.

This. Also, high water tables. And if they count domes, issues with leaks.

Regulations...