Overwatch
Blizzard has as large an audience, if not larger than Valve on their own launcher platform. Unfortunate, but it's better business sense for Blizzard so that Valve can't take any store fees on top of any sales they make on Overwatch.
Halo PC and Halo Custom Edition
These are in an odd legate right now between Microsoft, Bungie and Gearbox. I really doubt we'll see them on any digital distribution platform in the near future.
The older Need for Speeds aswell as being optimized to run on newer operating systems.
EA has closed/merged a lot of the original studios responsible for these games, meaning they would have to hire new teams to work on them, which is EXPENSIVE (especially since there's like 12 games leading up to Carbon). Furthermore, people never understand the amount of effort in making a compatible port; you have to completely dump and change the Windows/Renderer code, and depending on the game and how intergrated that system is, it can mean gutting the majority of it and having to rebuild it from the game up.
minecrafT!!!!
Valve would probably take great issue to the Realms and Card system that Mojang are using for payments. Besides, Microsoft already have it on their Windows Store platform, a competitor.
Halo Reach
Uncharted
Excusing Uncharted 4, both are console exclusives, fairly old and were designed for a different architecture to the PC. It's not going to happen.
sims 1
EA are nowadays very strict about making sure their titles stay on Origin (or uPlay, wtf?). There's also problems with compatibility here.
Halo 5 and Star Wars Battlefront.
Halo 5 is an even worse case that Halo: Reach in terms of exclusivity (Microsoft were banking on a killer app). Battlefront 2 exists on Steam already, but the newest title is another example of EA trying to keep their platform competitive.