X1/PS4 DRM is not that different from Steam's. I'd say X1/PS4 DRM of digital games is much more restrictive than Steam's, since MS/Sony don't offer backwards compatibility or any choice of hardware to run the games on. It's PS4/X1 or nothing.

Yet X1/PS4 downloaded games are more expensive.

Prices are all about what people are willing to give, not much else. If Valve would've made a closed system similar to X1/PS4, the prices would probably be similar.

Valve believes in open hardware platforms, so games are cheaper but hardware will be more expensive. MS/Sony believe in cheap simple proprietary pay-walled boxes with as little competition as porssible on their own platforms as possible, so games are more expensive.

I think its very possible Steam will be able to be streamed to Xbox One.  There has been rumors of Steam coming to xbox after people dug up coding back in like August of last year.  Windows 10 allows Xbox to stream to PC and other windows devices.  Windows 10 is coming to XBO so Xbox may be able to stream PC as well just like Nvidia Shield does.  So in theory Steam could come to consoles through streaming and i think it may happen 

With win10 coming to XBO, it could be. Just depends on MS/Valve

Could they? Yes. Would they? No. It would directly compete with their digital stores. Sony didn't even want that EA gaming service.

Doubt it. Steam is proprietary to Valve so it would have to be Valve that actually develops it for the consoles. It could help reach a wider audience but Sony and MS probably wouldn't like it because they would want part of the pie from sales of Steam games. So either the service woudln't be the same on all platforms or they would want part of the PC and Linux versions as well to help lower the costs on the consoles. That would still end up pushing up the price for everything on all platforms, which wouldn't make steam users very happy and would likely lead to less sales. There is also the issue of Steam generally being a better service than what is offered on either the PS or Xbox so neither MS or Sony would be happy about that either because it would eat into the sales on their services. 

As far as if it's technically possible. Yes, it is technically possible. Now to have all the games work, that's the hard part and the same issue that Steam is having with their Linux offering. Most of the games still require windows to work, so that's why there is far less offereings on the LInux version. It would have a better change of working on the Xbox than the PS4 since it shares much with windows as the PS4 usues its own OS that is not based on Windows. 

No...it wouldn't really work. Theres a bunch of reasons, but for one, many of the games that are on Steam but not on PSN/XBL don't have an ESRB rating because Steam doesn't require it, however consoles do. Additionally, many of the games are not optimized for consoles and don't meet requirements such as the ability to use a controller.

I'm sure there are plenty of other hang-ups, but the overall picture is that devs would have to go an extra step to make it work, and at that point, why not just put the game on PSN/XBL natively?

Also, there is the fact that this splits revenue another way, which would result in someone (likely devs) coming up short...

I could be wrong, but this doesn't seem like a likely scenario

it's like apple allowing amazon to sell apps directly on ipads as a substitute for the app store. it's not going to happen, even tho the ps4/xbone are basically lower mid-range pcs at this point.

Steam could be streamed to any device, the app just needs to be made and have the parameters set. 

From reading the other replies it would greatly increase revenue but decrease profits.  If Microsoft don't care about profits from games and want to have another go at taking over the living room they could try this. 

Could? Maybe. Will it? I cannot see why from Sony or Microsoft's perspective. They'd gain little to nothing and give up a great deal.

My hope is making it easier to port games to systems from PC. I'd pay extra to play games on my Vita or PS4.