I've never understood why people are willing to put up with garbage gear either. I'm not talking about the computer itself, but the things you touch.
You sit at this machine and use it for 8h+ a day. Why shouldn't you be in contact with things that feel good to you?
Nice screen (or two if that is your preference), decent keyboard, mouse that feels good. I think it is important.
Mechanics don't use dollar store ratchets, do they?
Give me a break. Software development has been going on for decades now on all kinds of hardware (how did all those Software developers survive all these years??).
You can be productive and get your work done on a single monitor, you just prefer dual monitors.
If my company only gave me dirty river water, sure water is good and technically I'll probably survive if it's free of parasites, but once you have high quality filtered water you don't want to go back to drinking from streams.
A single monitor is not a health hazard.
For some reason people here are purposely confusing "I can't" with "I prefer not to"
Even I use a tiling terminal application, but that still leaves me needing another display for the web browser and work chat, for instance.
Then those are preferences, not need. I agree a second monitor should be provided if asked, but in no way is it a requirement. I'm not alone in my preferences either. I learned to code in Turbo C where the line length was _puny_ compared to even this comment box here. I was probably more productive back then.
With great difficulty, and/or by having printed reference material in a readily reachable position - think program listings, magazines, reference books, paper notes.
On a related note, if you have never had a mouse with buttons on the side, I can greatly recommend trying it. Especially if you navigate through IDEs with your mouse and not the keyboard, i.e. you have one hand on the mouse and one on the keyboard and not both hands on the keyboard.
A related note is that I loathe garbage keyboards. If you make me type on some garbage rubber-dome with unbalanced and scratchy keys, I will not be happy.