Egosoft is phasing out the older linux ports so they can remake them. I guess there is an incompatible with Steamplay.

And now I'm crying because I don't own the collection on Steam so no Linux version for meeeeeeeeeeee. Or I'll just buy it again when its on sale.

I'm really starting to like Valve for all they are doing for the Linux and Mac gaming community. I might be a bit annoyed by some features of Steam, but if I can play more games under Linux I'm not going to slander it.