Take abcabc as an example
When we print a character, it COVERS all others along the way.
You print aa first. Then you insert b ,insert c,insert b,insert c.It takes 5.
In your case, you think you are printing aa bb cc and done.But the way it works is that: you print aa first. When you print bb,they are adjacent,so it becomes abba. Your next c could only cover up(replace) one of them,which takes three steps total and becomes abca. And you need to print b and c over again. So still, it takes 5 not 3 steps.
Otherwise the printers are not "strange" any more :-) Hope it helps.