when you learn to drive a car.... you can drive almost all cars... the biggest difference is with the manual o automatic gears....
when you learn to use a computer you should be able to use many of them whithout having to learn anything.
A car does one job. A computer does many jobs. Learning to do each job a little differently, adds up to a lot of learning. I don't know what "you should" has to do with it - I'm just pointing out that for all desktops that currently exist, you have to learn how to use it.