Never:
a. It costs money, I understand for something like a MMORPG, but for a RTS. You don't pay for Battlefield, do you?
b. I don't have a creditcard and won't get one for TW. Sides kids don't have creditcards either. And they are the main public.
c. As it's now it isn't worth it, and I doubt CA will be interested in doing much more for MP. As we calculated some time, of the millions buyers maximally 16,000 play MP. Is that worth it? No.