Not OP, but price and availability. Before about a year or two ago, it was a cheap-and-cheerful way to put some smarts into any project. Now it's impossible to get at twice the price, and the alternatives aren't quite there yet in terms of software support.

I still like reading about the projects you can do with it though. I find it inspiring for my own side things (even though fewer of them involve the RPi itself -- you can push microcontrollers really far these days!)