Steam (and other DD services) charges something like 30%. F2P games on Steam are also all cash store games that give Valve a percentage off in-game puchases. Either way, Steam doesn't work for free.

I agree that the client should be available for download. By the time of the PS3 release it'll be patched all to hell, so a fresh install would work more optimally, and it's a way to support their subscribers who bought a copy of the game with a broken install disc.