I like the openness of Ubuntu, since making the switch over 4 years ago It's motivated and enabled me to learn more about programming... And the lack of license requirements means it's come in handy for software testing, or trying out a free, open source solution as opposed to buying a piece of software for one-off tasks.
I want people to see Linux can be used as a desktop, but I also get fed up of how windows struggles under more and more load and how windows handles updates. Also for business, Ubuntu is preferable to other distros, not only for the "just works" factor, but that Ubuntu is the common desktop for vendors who are offering windows alternatives to their software; so it's easier to get troubleshooting tips and workarounds when you're just needing to get your work done, rather than try to root cause the issue.
I have tested other distros in the past like Fedora and OpenSUSE, but at the time the were a lot of issues for me like broken dependencies or other minor things that I just didn't have time to figure out how to fix when my primary concern was I need respond to emails, and get things done by deadlines. I have no idea if this distros have caught up with Ubuntu.
I did use Mint for a long time and it also "just worked". I also currently use Ubuntu Mate in a VM on my work laptop because I found unity didn't work well with the low spec.