But take a room full of kids and get them to write a program that blinks an LED, or drive a simple 'robot' forward, and it's awesome. Easy to use. I've never burned out a board (even driving considerable current through them). Things are tolerably well marked. Lots of teaching tools. Lots of different suppliers of easy to connect motors, servos, lights, sensors, etc.
For the same reason, if you are not an embedded engineer, but need a simple micro-controller to turn something on an off like a heater in a chicken coop, it's fantastic. And if you want, buy the $5 knock-off Uno. It should be the same, except that it doesn't support the (now defunct) foundation.