Swapping from Steam to non-Steam client?

[Valkyrius]

It's been confirmed that you have to buy the game off Steam in order for it to work, unfortunately I doubt they'd release a Steam physical Collector's Edition.

http://steamcommunity.com/games/39210/announcements

Yup, I quoted from that earlier. However, I would like to hear from either SE or Valve, officially, as to why one whole community has been excluded.