Can't you do that any more?
I remember my old Nokia could be controlled by a cable to read and send texts.
Unfortunately, today's phone can do that without a cable, making the process less complicated.
What kind of "work" do you do on a phone?
Probably Bing searches
But Bing is only for porn... oh.
My guess it that they were doing a "two birds with one stone" strategy - using this project as an excuse (and test-case) for the translation layer, hoping that some devs would take this opportunity to port their DX9 games to Linux because of it, thereby improving the value of SteamOS.
Another option is that they didn't write DOTA2 from scratch, but reused an existing engine. Which in turn was based on some previous works, and at some point Direct3D was used, and remained there the whole time.
Arithmetic is being able to count up to twenty without taking off your shoes. -- Mickey Mouse