Indeed, the market has spoken, and the 2016 MBP is a big sales hit.
I'd say it's called pent up demand and they've got nothing better. But to go off of earlier reports, apple was "taken back" by how many people actually ended up buying the 2015 once the 2016 was released.
I know I'd go with a 2015 if I was in the market, but my 2012 (pre-retina) just keeps chugging along. Honestly, the last rev of an Apple product before a design shift is always the best. That's why I'll be going with the 7s over the iPhone 8, assuming both are released this fall (always go with the S release).