I think it has a lot to do with how high the price of scrap steel was last year. People were advertising for any scrap metal. I am sure a bunch of bikes went that route. Around here, we have a spring clean-up week. You put your junk out by the curb, and the garbage man takes it away as long as it isn't hazardous or building materials. Used to find all sorts of things then. My kids got more excited for that then Christmas. When scrap went up, it was like a parade of trucks going up and down the streets picking up anything that was metal. It got so bad that they stopped doing it all at once. Now you can put stuff out anytime, you just have to call them and let them know.
It also helps that we live in a town with a steel mill and 2 scrap yards. We don't have to drive far to cash in. Prices really hit bottom last fall. It wasn't worth the gas to go pick up the stuff. Now I find a few bikes sitting out from time to time again.