That's easy, just look at the games around. AI money was invested in other things, as, except in RTS games like Mummelmann said, other genres have a quite bad AI(covered by great animation effects which does fool some people into thinking that's good AI).

Graphics mostly sell the games/systems, not AI, that's the simple truth, just look at the PS4 announcement, the praise for the system was mostly based on "The Graphics"

Don't expect much change in AI next gen, it's still easier to produce pretty games and get the instant Hype, than go all abstract with great AI and hope people will notice, fact is AI takes a LOT of resources that most modern publishers would rather not risk for modest gains in sales, pretty graphics gives you the biggest return for your dollar

The Hype for a pretty game can get Huge, the hype for amazing AI is modest at best

I personally want better AI over graphics, but it's graphics that sell, so I don't see many changes going into "next" gen