Expansion Question

[Mission]

...But you can still play the game you bought the expansion for on the system you bought the expansion. I really don't see why you need to play it on 2 different systems, what is the point? Like really, I don't understand the waste of money in having the same thing on another system when one is all you need.

I play on 2 systems cause sometimes I don't want to sit at my computer to play. Like when I'm doing random things such as crafting. When I raid I play on my pc. And I can play on my vita anywhere.