In factory work, being on time matters. Because you're taking a widget from the person to your left, adding value by performing some operation on it, and passing it to the person on your right. If you're not there, and there isn't someone who can fill-in, then the assembly line stops and the firm ships no widgets.

Be late often enough, and you get fired.

I'm very glad that software development work isn't like that, btw. I am not cut-out for Taylorism. http://en.wikipedia.org/wiki/The_Principles_of_Scientific_Ma...