I do think that, really, the single biggest factor is the internet. Social media included, but mostly the ability for folks all around the world to access obscure information that would be impossible to learn without a close mentor. That being said, the internet has been accessible to most of us since, what 1995? It's my understanding that although wet-plate popped up on folks' radar somewhere circa Sally Mann's "What Remains" and "Deep South," things have really started to pick up lately. I did a few keyword searches with google, and most wet-plate related keywords didn't have enough data to chart until well until 2009. A snapshot of the collodion.com forum from 2011 shows that their membership has doubled in under a year. And I know the B&S is totally swamped with orders for wetplate items. Perhaps we've just reached a tipping point.
I also think that nowadays it is very difficult for someone who isn't exceptionally gifted to feel they have mastery over anything at all. And feeling as if you have autonomy and expertise in something is very important. An entire generation has grown up surrounded by things and processes and ideas they can't fully understand, and could never, ever make or even modify, except for a gifted few. Take for example an Iphone. It gives you entertainment and keeps you connected, and on a superficial level gives you a rush of excitement from the sheer thrill of holding an advanced piece of technology. But, do you really know how it works? Could you design the chips inside, or program the software, or distribute hundreds of millions of them across the world? Unless you're Steve Jobs--no. And I think on a gut level this makes a lot of people nervous and sad. Including me!
Wet-plate is something I can understand. With wet-plate I can be a craftsman--a group of people who pretty much died out a long time ago. And it's something that's almost totally out of the hands of corporations and the ad-machine--at least for now!