No offense, but Casa Grande was, until recently, a modest farm town with modest incomes. Ag labor just doesn't pay that well and pools are expensive.
In contrast, here's a random middle class neighborhood in central Phoenix[0], the fifth most populous city in the US of A. You'll notice some of the streets have a pool in every single backyard. When you zoom in on the higher income neighborhoods, like in Scottsdale and PV, it's rare to see a backyard that doesn't have a pool.
MOST people don't grow up in higher income neighborhoods. While it may seem odd to you, who probably makes well north of $100k/yr on your salary alone, let alone a spouse/partner... Most houses, in most of the Phoenix area don't have pools.
In contrast, here's a random middle class neighborhood in central Phoenix[0], the fifth most populous city in the US of A. You'll notice some of the streets have a pool in every single backyard. When you zoom in on the higher income neighborhoods, like in Scottsdale and PV, it's rare to see a backyard that doesn't have a pool.
[0] https://www.google.com/maps/place/Phoenix,+AZ/@33.5352177,-1...