> What I notice is that despite aspect ratios becoming wider, the monitors have pretty consistently also become taller in absolute measure.

Dell 3007WFP and the Apple Cinema HD display were both ~16" tall. They're over 15 years old now. They were a expensive at the time, but they're still taller than most modern 16:9 and "27:9" displays available now.

>What I don't understand is why I'd ever want 1920x1440 (4:3) monitor over 2560x1440 (16:9) one, unless I'm really space constrained

I want a 4k 4:3 screen. If you're going to dream, why not dream big? 3840x2880 please. I have a CRT that syncs to 2560x1920 and I already enjoy it for a few odd things.