Steam is missing a few major titles (mostly from EA and Blizzard), but it's one of the most complete digital download services. It also seems to be rather indie friendly.
But all types of digital piracy are connected by similar economical choices of the consumer.
Valve, iTunes, Spotify, Hulu, and Netflix all combat piracy by being more convenient than the alternative. I'd much rather use those services to get what I want.
However, if content is not readily available digitally, then plenty of people have no problem getting that content via piracy. And the reason they do that is simple: the risk of getting caught and punished is vanishingly small. Even when the RIAA was at it's most aggressive, the number of people sued was trivial compared to the people who were file-sharing.
I think it boils down to this: if you are not in the marketplace, your stuff will be pirated. So get in the digital marketplace and "close the buggy-whip factory" already.
Steam missing EA's titles is a recent development caused by EA starting their own competitor, Origin.
It remains to be seen whether Origin can gain any traction as a (currently) single publisher platform, but it is required by their new releases, just like Steam back at Half-Life 2's release.
Steam is missing a few major titles (mostly from EA and Blizzard), but it's one of the most complete digital download services. It also seems to be rather indie friendly.