The ethos of suburbia is conspicuous consumption, especially conspicuous consumption of land, and actually using it to produce something useful makes it more of an investment. This is also why it's illegal to carve off part of your house and rent it out, generally hard to keep boarders, illegal to actually engage in any kind of business in your house, and so on. I guess the ideal is to be like the landed gentry in their country manor, which also explains the obsession with lawns.