As a programmer:

• one 1080p screen for work chat/email
• one 1080p screen for code with 3-6 pages open simultaneously (approx 80x24 or 90x40 depending on whether the file tree is also open)
• one 1080p screen for a terminal with 4-6 terminal sessions displayed (80x24)
• one 1080p screen for reference documentation
  • or more 1080p screens for even more documentation as rabbit holes in documentation can go quite deep

...and that's before even more screens for monitoring services, CI status, rabbit holes in documentation, etc.

Then there's video chat. It gets really fun when someone asks "@inetknght, can you share your screen?" during a video call. Then I have to pick which screen gets shared and hope it's the right one. It would suck if they how many emails I ignore. I currently have 15,070 unarchived emails in my inbox spanning over a decade. I'll get to cleaning that inbox when the bug reports stop coming.

Plus, I sometimes run VMs fullscreen. It's best to do that on a dedicated monitor. Especially if there's multiple VMs running. Otherwise good luck finding the real desktop!