Arguably it has. Weaker 2012 than 2011-- despite two extra months of reporting in 2012-- can be attributed to any number of factors, including the popularity of mobile versus traditional dedicated handheld gaming platforms and a weaker slate of releases in 2012 versus the year prior.
It's one hypothesis, and by no means the only recognized correct one.
I have a feeling the nature of the Vita made it more susceptible. A lot of the appeal with the PSP was how it was a neat, cutting edge piece of tech the likes of which we hadn't seen before, not at a relatively affordable price anyway. That, and Sony was at the top of their game and appealed to a lot of people that didn't care for Nintendo stuff while the DS looked to be a potential disaster. These really aren't qualities that hold up as well now: if you're all about cutting edge tech the Vita may be novel, but it's not a smartphone or tablet even if the guts are roughly similar, just a dedicated game machine, console players may well be more apathetic about handhelds as a result of phones/tablets/REALLY cutting edge graphics than they were 5-8 years ago, and it's not really that cheap especially when you consider the Kindle Fire (HD) and especially the Nexus 7. That, and Sony IS kind of a wreck these days, and while I imagine this has been something of a problem their whole life it really seems to be showing now how badly coordinated the regions seemingly are thanks partially to how important online is now.
Nintendo meanwhile always focused more on cheaper handhelds that did ENOUGH, and hit a wider audience that can be more receptive to the idea of having a handheld for their gaming device, and in the case of kids may be too young to really be trusted to have a tablet/smart phone by some parents (I don't think I'd be very comfortable getting them one unless I had piles of cash, and even then a pure physical or physical/digital hybrid library is more practical for content control than pure digital). I think that's allowed them to be more resilient, plus I figure among core gamers either A. they don't care so much about cutting edge visuals so they're content to get a 3DS so long as there's games they want, B. it's where all the games they really want come out, or C. they'll get just about any relevant gaming device, and with numbers like that the 3DS IS relevant regardless of what some may say, at least within the context of gaming devices.
