Is it that they’re named differently in different places or simply don’t exist? I think mostly the latter. You are going to find them more in municipal areas that spend money on parks and recreation and have a fair number of children like here.
You’d think most grandparents would have taken their grandkids to splash parks if they existed in the area...
I don't think that's it. As I mentioned I'm in the Atlanta metro area not far from Truist Park where the Braves play and if I leave through the back way out of my subdivision, I can turn right, and then right again into the entrance to Six Flags White Water | Georgia's Most Thrilling Water Park. That must be why I didn't know what a splash pad was.
But actually I think as you alluded to, that is not what it would be called down here.