Why? With PC sales alone they went from almost bankrupt and heavily in dept to prosperous developer, debt free and so much money they opened new studios and started work on two new games. Console sales and market is hugely overrated and overblown, as the awesome new thing that is Steamspy shows us. The Dark Souls franchise sold roughly 40% on PC alone. That's with Dark Souls 1 coming a year late on PC and being the shitiest port ever. The other 60% is achieved on four consoles. Same with Tomb Raider 2013. Also 40% on PC and the rest divided on four consoles. Same with Hitman Absolution, Dishonored, etc. PC is in fact pretty huge and no, you don't "need" console sales for a computer rpg.
All will be good if stuff keeps happening as it does now. But seeing how they all of a sudden think controllers are so awesome and they all couch play it now over there, it's all but certain that future projects will have a game design closer to what pads and console audience want. I mean, if they had a problem or something was more difficult to translate on pads with Original Sin, you can be sure they'll make it more pad friendly in the future from the start. Why design one thing for PC and another for consoles, they will think. Time consuming, more expensive. Let's just homogenize from the start. God damn consoles.
You seem to not understand one thing. Mac forms like 5-10% of marketshare on PC market. Linux - similarly. Despite of it, more and more developers are making OSX/Linux versions of their games nowadays. The reason is fairly simple - lately it became much easier to do it as far as technological matters go(it's also cheaper). These games would easily survive without having OSX/Linux ports, sure, but porting became so easy, that there's no reason NOT to do it.
The problem with most franchises going to consoles lies in mentality. When developing AAA multiplat, companies like Activision or Ubi think about it like:
"Okay, we have a game for console gamers, but there are also some people(reasonable amount of people to be fair) who would want to play the game on PC's. It's not our focus, and don't try to compromise the console versions for favour of PC version because while there's decent amount of them, they're not our main audience"
Which makes sense if you think about it.
The smaller guys, who tried to turn PC-typical games into console games(Firaxis for example) were like:
"Okay, we have game for PC gamers, they'll probably our main audience but seriously, if we make the game more console-friendly they will be only little bit mad, but we will steal CoD so many millions of sales this year that it'll be worth it!"
Didn't worked for Civilisation:Revolutions, nu-xcom didn't flopped only because the audience of such games was starved as fuck, still didn't get lots of console sales, that says something I guess.
This approach seems to be replaced by:
"We have a PC game, for core PC gamers, but we want to port it to console as well. Make the game the best you can for PC, and try to make it playable on consoles, but no compromises because console gamers aren't our main audience".
Finally, the proper mindset for multiplat development should be:
"Our game, due to its genre/core gameplay, brand image and variety of other factors should be targeted at <platform>, we shouldn't ignore the other platforms, but don't compromise the quality of <platform> version of the game by design because you want to make them fit/better on other ones, they're not our main audience."
Where platform has to be understood little wider - as console, mobile and PC.