Most big developers while looking at these systems may see three very different situations(in regards to porting), but when they make a game for all three, the final product isn't to far apart performance wise(maybe it's more work, but they see the benefits in the end). Of course if you have a monster PC, that is always going to rule, but most developers know that's a niche market compared to a large consoles installed based, especially if it's been around awhile.
No, it's not.
http://steamspy.com/#tab-graphs
Number of current Active Steam Users: 212 Million
Current Playstation 4 hardware unit estimate: 49 Million
Current XBox 1 Hardware unit estimate: 25.5 Million
Current Wii U Hardware unit estimate: 13.7 Milllion
So to review the current number of Active Steam Users exceeds the hardware unit totals of any console ever sold, and is over twice the entire combined 8th Generation Home Console market. Of those only the Playstation 4 can makes claims of being financially health, and it's top ten games by units sold are:
CoD: BO3
GTA V
FIFA 17
FIFA 16
SW Battlefront
CoD: AW
Fallout 4
Uncharted 4
FIFA 15
CoD IW
So to review that's 3 iterations of FIFA, 3 CoDs, GTA V, SW Battlefront, and Uncharted 4 as the Playstation 4's top ten. Out of 1316 Titles the PS4 drops below 1 Million software units at #83, below 500k at #133, below 250k at #189 and most would struggle to name 5 solid exclusives on the platform. In turn there are memes about the things collecting dust.
Along those lines currently ~95% of the XBox One's games are available on PC with the exceptions largely being Kinetic games. The Playstation 4 in turn stands at ~91% of its library being available on PC. Legitimately bad ports in turn are rare enough that Console Gamers are still hanging onto referencing Arkham Knight, despite the port having been fixed around a year ago. Of course part of the reason Steam's library is as big as it is, is because of its massive pull of all the games from all the platforms which has helped fuel the growth of Steam and the associated trends.
Estimates in turn put the size of the average Steam library significantly higher, and the library of games on Steam alone utterly dwarfs those of any home console, with top sellers tending to actually represent diverse genres.