Kresnik on 25 September 2012
I think many publishers think they can't justify the price of an AAA single player experience these days, so multi-player gets added to 'increase' the value
Personally, I wouldn't buy a 12 or less hour single-player only experience these days, but that's more to do with my personal finances than anything. If I had the money I'd buy many more things new - right now I justify a purchase by it having insane replay value, or buying it months after release or pre-owned.
In regards to the actual experience, though, I think I'm beginning to enjoy single-player games more again. The novelty of multi-player is fast beginning to wear off, except for co-op which I still enjoy.
