Steam is hugely important in this regard because it shows how catastrophically wrong the old guard in games, video, music, and other media are. By default, people accept that paying for things is right. The challenge is to make paying for things easier than not, and to not actively sabotage the social relationship that makes customers prefer paying for things to pirating them. Steam has actually done a reasonable job at that: by contrast, DRM and MPAA/RIAA-style tactics are, to understate, recent-severe-head-wound-level dumb business decisions; they say to customers "our relationship with you is fundamentally antagonistic." Once that social message has been sent and supremely customer-hostile services like Ultraviolet (and worse earlier systems) established, piracy becomes massively attractive and the MPAA/RIAA-style cartels have cut off the ability to have a reasonable conversation about it.

I agree with this - low friction is what makes Steam successful. (Personally I stick with HumbleBundle as the Steam client has traditionally sucked ram).

Steam lets players join multiplayer games with their friends -- seamlessly merging a friend list with game servers across all games. That's a strong incentive to use Steam.

So what about other forms of content without online multiplayer like say, TV shows?