It doesn't worry so much when cities sprawl onto deserts ...
While it would seem like using land that's apparently worthless for anything else as a place to build, in reality much of the desert/arid spaces are what they are because of lack of water, which is an obvious problem, but also because the soil doesn't percolate in a way that permits any sort of effective septic system for disposing of wastes and runoff.
In the mid 60s, as an example, Phoenix Arizona imposed a "total ban" on any new septic fields, thereby effectively banning any and all development within about a 70 mile radius around the city already in existence. When originally announced, that ban was to be for 30 years - renewable. I haven't heard what they did when the original blockade expired, and of course developers with enough money to dump into it (or slide under the right tables) managed to continue some new building in the area.
Around the same time, Denver Colorado was talking about "population limits" and "population growth avoidance." At that time they considered water resources "inadequate to sustain the existing city within n years" (3 < n < 5?). They had already far exceeded the "septic limit" of nearby soils, but didn't seem to care much what kind of sh*t flowed downhill 'cause that was "just Kansas down there anyway."
There are very few places west of the Mississippi in the US with arable soil and enough water legally "owned" by anyone who farms it, and the only way crops get grown now is by stealing water from somebody (everybody?) else. A developement, even if it doesn't grow anything but hoodlems and delinquents still has to have water, and in nearly all cases has to steal to get any, so it really makes less difference than one might assume whether they use the poor soil or something more fertile. If they're there the good ground can't grow anything, whether they sit on it or beside it.