You're right,they didn't.
The vast majority of people who run with Android of any flavor never root them or run custom roms.And the Moto X truly needs to to run the best.
Truth be said,the vast majority of any Androids need to be and all IPhones need to be jail broken to be at their best.
To me ,that is what is so appealing about WP, it runs better out of the box without having to over clock it because it's designed to be.
It's rather funny to me, the majority of the world uses Windows over anything else for desktops and servers, just think when everything in Windows is fully integrated, whose phones will be leading then?
Mac