I wasn't necessarily looking into being asked, but since you did ...
I got 15 when it was a few bucks off after release (All Star Game?), and had a league on the Pacific Coast in mind, but I never got around to make up my mind on where to place teams, to design a schedule, and so on.
Then a couple of people in the office ... "went to the DL"
... and I worked intense overtime for the last six months of the year, which made my Raccoons dynasty plenty enough to worry about.
And now it's February, and I still haven't installed 15, and I can't be bothered right now, although it would be fun to manage a winning team again, which I didn't get to enjoy since July, either. But who says my team in a different league would be winning. Maybe I suck at managing.
And since I have 15 sitting around anyway, why would I buy into 16, regardless of the features? I've come to hardly being able to care less about it.