There's been fourteen different major winners over the last four years (McIlroy and Mickleson twice). Seven missed the cut: Duffner, Simpson, Els, Schwartzel, Bradley, Mickelson, and McDowell. Watson will probably win, Mcilroy is tied for eighth, and Scott tied for fourteenth. The other four (Clarke, Oosthezien, Bradley, and Kaymer) weren't in great form coming in but made the cut.
There just aren't many seasoned winners playing well this year and there have been a couple of quirky late career major winners over the last four years.
It's more of a reflection of the current major champions than the golf course.