Firefox

that's interesting because frankly I feel the opposite.vertical screen real estate is at a premium, it's already common to have a horizontal taskbar and/or menubar eating into the desktop space, and then any browser UI like address bars eat into it more. Meanwhile most websites I visit are filled with whitespace on either side and always require scrolling down, often infinitely scrolling down, so the more vertical space the more you can fit on screen without scrolling.

To put it another way: I rarely full screen my browser because making it wider doesn't help, but I usually have it filling the maximum vertical space. Granted I'm on an ultra wide making this problem worse, but even at work on a 16:9 I feel the same way