Why Linux Mint and not [insert distribution name here]?
Because Linux Mint is really a begineer-friendly distribution, but can also expand when needed.
It features the Cinnamon Desktop with a Windows-like UI. Cinnamon is also very customizable, and most users
switching are looking for freedom.
I know, this is all the hype now. But, most users switching to Linux are coming from Windows,
and Elementary OS is more like Mac OS X.
Zorin OS distribution has a WIndows-like UI, but has a Pro edition and a "customization" app, which,
instead of allowing users to choose DEs, applets and GTK themes, it only allows pre-made layouts and
Zorin OS is just not as good as they describe it on their website.
Ubuntu looks more like Mac, and it is commercial. What are switching users looking for? Freedom.
Ubuntu completely negates that.