In Niagara, despite access to 2 Great Lakes, I always attributed high pool ownership to longer summers than most of Canada, and the high paying industrial tax base that once existed.
So many I grew up with, in 2 parent (double income) families, either had a pool, boat, or cottage (usually passed down thru generations).
The trifecta was a family that had all 3. Good paying factory /unionized jobs and relatively inexpensive housing allowed for most families with both parents working to build a great life
Pre Google maps/Earth, my friend's father that was a Vietnam Vet/A-6 Intruder pilot took me, my father, my friend for flights in a rented Cessna or Cherokee plane and it was then I realized how many swimming pools there were.
Here's my old neighborhood (using Google Earth)
Across the border in Buffalo/Western NY, pool ownership is also high. We used to get inundated with pools and spa commercials from Buffalo TV channels