It's simple... (Score 1)

The idea is to get youngster interested. You can't just say here, start programing something, kid. Building a machine is a good introduction to computers. After you make one, it's only natural to next want to "make it" do something. Hence, wanting to learn to program.
Slapping some software in front of a kid isn't much motivation. Learning a bit of what a computer could be made to do is.