Don't forget to look up the old Heathkit Hero1...
I so wanted one of those when I was a kid!
Robots, Arduino, computer programming in general... it's all for the same reason, really. As someone already said, people like to see their creations act in the real world. It doesn't matter if the AI is dumb as a box of rocks. Seeing your creation do
anything under its own power apparently satisfies some kind of psychological need. I imagine the inventors of the locomotive and other 19th century automatons got the same thrill as a kid today watching his DIY robot avoid obstacles and move about, apparently of its own volition.