The game made the leap to steam, but it doesn't offer subscriptions outside of Xolla.
I will buy subscriptions through Steam, when they're available.
I do not want a Xolla account and will not be making one.
Visible subscription offers on the steam store page would also show a legit belief in the game, thus reassure new users confidence in the experience.
What's the cut on Steam, anyway - 20%?
Edit .. you know, I've just checked the subscription price and it's as low as $50 for a year. That's low enough to consider Xolla but Steam would be a great addition.