It's repetitive, easy to take apart and fix, simple to use, and has an understandable function. And, it has an immediate, and visible reward for its use - there's dirt on the floor you want gone, so you run the vacuum over it, and "poof!" there's no more dirt.
How many times has your vacuum not gotten something up....so you bend over, pick the thing up, and throw it in front of the vacuum to try and get it again? Would be a lot easier to put the bit of whatever in the trash, but no.... I catch myself doing this, occasionally.