Probably different staff. They changed a lot from PS2 to PS4. Not to mention that they had to sacrifice that framerate due the PS3's radical change of architecture.
I think it's kind of the first time they can seemingly have their cake and eat it. PS1 was at a significant technical disadvantage to the N64, and Sony was so dedicated to pushing richer 3D rendering that almost nothing had the luxury of being 60, in fact, right now the only 3D PS1 game I can think of that was 60 was Omega Boost, there must be more, but they were rare. Then in the PS2 era ND were doing the Mario 64 thing, later with a little GTA in there, very impressive to have them running at 60, but in that sense it was also dictated by the tastes at the time, it was the PS3 and the jump to more graphically demanding visual presentations that forced almost the entire industry to target 30.
Before the new consoles were announced, there was a lot of discussion and fairly heated debate surrounding what developers would do with this new found huge GPU performance, some seemed to think basically PS3 games in 1080p/60fps, some thought really graphically rich visuals at 720p/30fps. I always imagined a mix, that 1080p would be standard, because scaling artifacts are hideous, but certainly still mostly 30. I don't know that anyone really thought we could have 1080p/60fps and a very significant graphical leap, it's why that UC4 trailer being real was so hard for people to believe, it fells like you're seeing no compromises, for the first time.
(my wife will ask for divorce at one point, but oh well 
