Is 16:10 too much to ask?
Yes.
We are talking gaming monitors here. The trend in gaming monitors is to go wider. There are quite a few 21:9 options available now, and in the near future. Just 2 years ago there was 1 21:9 monitor available, a 29" one, which is rather small. And it was targeted towards people who wanted to watch wide-screen movies, without black bands at the top and bottom of the screen. But that changed. The 21:9 monitors are now targeted towards gamers.
I'm not sure yet I like 21:9. I've seen a 21:9 in real life only once. (The 29" one). I have a 27" 16:9 monitor right now, but I used to have a 24" 16:10 monitor before that. I liked the 16:10 better than my old 4:3 CRT. Both for games and movies. But even for the desktop 16:10 seemed nice. When I switched to 16:9 I concluded that there were upsides and downsides. E.g. I used to play a lot of WoW. Having that extra vertical space allows you to have actionbars and other elements of the HUD at the bottom middle of the screen. When you do that on a 16:9 monitor the viewable area gets very little vertical space. Using the desktop (for browsing, or for work (programming)) felt slightly better with 16:10, but 16:9 was certainly acceptable.
I've started programming again recently, and on a 16:9 monitor, the natural thing for me is to have 4 open (terminal-emulator) windows (with a shell or cli). But that means my "main working window" is not in the middle of the screen. I realized that if I had a 21:9 monitor, I could place my editor (emacs) in the middle, and have terminal-emulator windows to the left and right. That might be the perfect setup for the work I do. So my next monitor, which I will be using for both games and programming, will most likely be a 35" or 34" 21:9 monitor.
I understand your preference for 16:10. I used to have that preference. But I expect the size to become less and less popular. Certainly for gaming monitors.