Interesting. I feel like the majority of toilets (in my US city) have both buttons and it's been that way for almost a decade.

The only time they don't is when it's a toilet that's over 10 years old.

I could be wrong, especially since I mostly just use my own toilet (has two buttons, is 6 years old) or a urinal.

Maybe it's because in the northeast rains so much that people here think water is unlimited