Ive been meaning to say this but I never got around to it.
If you have a physical PC game you can put the key into steam and it works just like a digitally purchased key. Tried it with Supreme Commander and I even got the Forged Alliance expansion which I don't even own. Pretty cool.
Its funny because when I bought this game it barely ran on my pc.
Which by the way, to me thats why rts kind of went downhill for a long period of time. They started making command and conquer and total annihalation in 3d engines and (especially in the case of supreme commander) extremely hardware intensive. Then we see the rise of Dota and LOL out of that genre which even a potato can run. Thats what makes PC gaming great imo, not this master race nonsense. Back then it was even more accessible than console gaming. Its no coincidence rts became less popular as the system requirements went up.
I actually think, in a way, the array of widely varying games is what makes PC gaming special. Games like Supreme Commander are niche for their grand scale that by necessity requires a lot of CPU power to run. PC has such a vast library of games, and they have so much versatility in terms of budget. Aside from the huge memory leak problem, Forged Alliance was fantastic.
What truly killed RTS IMO is the lack of adaptability and yes the casual strategy games pushing them out of the picture (although they started to die before that), although I also think there is a certain amount of industry bias against them. There's a ton of gamers out there searching for another good RTS, but they just don't make em like they used to. Personally, I've really enjoyed the indie game Sins of a Solar Empire and sunk hundreds of hours into it. Blizzard is still making great ones in Starcraft 2.....but I'd kill for another RTS Warcraft.
While I do see your point, I think the biggest blow to PC gaming in recent memory was the mainstream switch to phones, laptops and tablets as the primary way to experience personal computing. It's pretty easy and cheap to upgrade your already existing desktop PC with a graphics card for some light to moderate gaming, but not so easy on the devices most people have nowadays.
That said, PC gaming is still alive and well and easily the best way to experience the majority of games IMO.