I imagine this is both part of Steam's gradual drive to become an all-things-digital storefront and reflective of the fact that it's happy to take 30% of any game anyone wants to sell via it, thus encouraging more people to make games is in its interest, but it's definitely an odd one.
The latest addition to its digital racks are software tutorial videos; you can pay for instruction in the likes of Blender, zBrush or 3D Studio Max. Conceptually not a terrible idea, but fairly expensive given guides can be found for free and your YouTubes and what not.
Prices at present range from £3.99 to £10.99. I imagine these are the professional tutorials of a higher grade than the average microphone mumbler's ad-supported effort, so may well be of more use to people who are really serious about getting better at this stuff. Right now there's not a lot on there, however, which at least puts it in line with Steam's rather thin general video store. The biggest names on that right now are the Mad Max series and Indie Game: The Movie, accompanied by loads of shorts from aspiring directors.
I suspect it's all part of a broader plan to make that side of Steam better-populated, but the ongoing lack of a download option seems like a huge oversight. Yeah, I know we're the Netflix generation and all that, but tutorials especially seem like something you want to have on a hard drive so you can go through on a train journey or something.
Given that Steam is the defacto storefront of indie games (or at least those hoping to earn a bit money) and also many of the leading game dev tools, hosting tutorial vids makes a lot of sense - I'm just not convinced that this is the best approach.