I have to say that your question caught my attention simply because I, too, am late to work. I usually am no later than 5 minutes late, but you would think it was 5 hrs by the way my manager acts. I have a son with oppositional defiant disorder and never quite know what my mornings have in store for me. I do not think it is a big deal when one is late as long as they get everything done expected of them. I don't think it has to do with inconsideration for our coworkers, either. I do think that because we would not be mad at our coworkers for this, we expect the same understanding from them. There are too many other important things for people to worry about in this world.