Among the Trees: People where people ain't supposed to be
It's not so much that cities are built where people ain't supposed to be, as that presumes a "supposer" to make those value decisions. In the case of cities, they grow where people congregate for whatever reason.
In the case of Phoenix, Arizona, people came there to vacation and to avoid the cold and allergies of the northern cities. Once land speculators and real estate agnecies were involved, it was all about moeny, and what do you need to make money in the desert? Water. That's why the Colorado dries up before it gets to the sea.
There is nothing wrong with people living in the desert, as long as they live there on the desert's terms. Making the place just like the place everyone left, including the same trees that cause the allergies that people flee from, is, not worng, just absurd. Such an arrangement can only be temporary, until cnditions change such that a city is no longer possible.
People must live in place, just as animals do.