"Why would anyone want to use Linux as their everyday desktop (or laptop) operating system?"
For me, I find non-Microsoft web development much easier on Linux that in Windows. I can set up a dev environment with web server and database all native and local and for the most part it Just Works. On Windows I find I either have to still configure a Linux server VM and set up my stuff there to write code on Windows and target the VM server, or go through some sort of WAMP setup. But I never feel like the various pieces running on Windows are as good as their Linux counterparts which is where the final product is going to run anyway. Java development, too, seems to just work better in Linux.
That said, after running Ubuntu for a couple years on my laptop I reinstalled with Windows 7 and have been there ever since. I originally just wanted to play a Steam game and it just wasn't working under Linux. But I also grew tired of having to hack things and run scripts from the Internet just to make things work. Just off the top of my head I remember dealing with:
graphics drivers for my Thinkpad T500
CUPS pdf printing that just disappeared and kept needing to be re-added
wrestling with browser plugins - things would work with Firefox but I'd have to play games to get them to work with Chromium
wrestling with getting any sort of Citrix plugin to work on 64-bit so I could access my employer's network