This has definitely been an excellent point since launch, and was the reason that I wasn't expecting any AAA games for the first year and a half. But I feel like its relevance is declining now as the PS+ library has filled out and matured, and as most hardcore gamers are already on PS4 (or XB1) as evidenced by the sales split of MGSV.
If you look at the price of launch games now, they've pretty much cratered. No one's buying those games any more. On top of that, there's a whole bunch of sports games and annualised franchise games that have been usurped by the next yearly edition, where no one will be buying the old ones.
Of course, that just raises the next issue - we used to get sports games and annualised sequels but these days I feel like all publishers want their own PS+ like EA created with EA Access and therefore there's no way they're giving their games to Sony.
I used to really, really look forward to getting sports games on PS+. That dream is pretty much dead. And I really did expect to see Assassin's Creed Black Flag by now out of all the annualised series games. We've gotten AC on PS+ before. But even thinking about that raised yet another issue. Games improve so little these days from year to year, and take so long to beat, that perhaps Ubisoft would be worried that Black Flag, rather than driving sales of their next AC games, would simply satiate gamer's thirst for that kind of game for a year on its own? Just one more reason NOT to put your games on the service, I guess.
I'm wondering if the reason is cause microsoft now has the ad rights to the assassins Creed series.