I ask this question because I see a very little activity on a ROMs forum, I didn't check other ones.
For example my previous phone, Mi A1 (Android One) has an official builds for most ROM, even my wife's Mi A3 has much better activity. I had bought Pixel because I'm a Google fanboy and its cheapest Pixel available.
My own answer: people with less budget just buy Android One phones (like Mi A* line), people who want Pixel buy a full phone, like Pixel 3 (without a) or 4.
For example my previous phone, Mi A1 (Android One) has an official builds for most ROM, even my wife's Mi A3 has much better activity. I had bought Pixel because I'm a Google fanboy and its cheapest Pixel available.
My own answer: people with less budget just buy Android One phones (like Mi A* line), people who want Pixel buy a full phone, like Pixel 3 (without a) or 4.