There's just too many of them! Many of them very good!
But not only are there hundreds of distros, with dozens of popular ones, but they each have multiple desktop environments to choose from.
Mint or Elementary? Cinnamon or KDE? Or none of the above?
And then what? I get used to one flavor on my desktop while a completely different one is more suited for me to play around with on my Raspberry Pi?
I will be the last person to die in my lifetime.