I use them all because I want to not because of any need.
I compile Unix / Linux and have been a developer since 1992 working with a worldwide community to bring you the things you love.
I use android on my tablets and phone, I have 4 laptops running various flavours / Distros of Unix / Linux.
My shed network runs 2 linux servers and cnclinux.
My desktop is currently running beta testing versions of Windows 8-9 release 9.6 which will become windows 10 or windows blue whichever M$ decide on.
A good way to experiment is to run virtualbox within your current os, download and install your preferred distro and play init?
Here is a link to a howto for anyone wishing to do this.
Here is a link to M$ developer downloads where you can play init?
Robolinux will do all this for you from a nice gui for those who are kbd shy.
There are also Linux distro's with mac desktop so you can familiarize yourself before making a decision.