A gentleman shows up on time. “On time” means the time of the appointment, not five or ten minutes after that time. By showing up on time he shows that he is a man of his word, that he respects the time of others. As in all things, it is especially poor taste to keep those waiting who must wait; this applies to interviews with employees, lunch dates, in fact, just about anything. One might argue that it takes a certain amount of chutzpah, or perhaps just stupidity, to keep the boss waiting, but its more an act of dissrepect to keep someone lower in the hierarchy cooling their heels – its as if you’re saying that you’re a very busy man or woman, and you’ll fit in whoever is waiting when you’re busy schedule allows.
To excuse tardiness by saying how “busy” you are is a flimsy excuse, and implies that the only reason other people show up on time is that they are not as in demand. This isn’t true – the people most likely to run on time are the people with the most to do, who are most concerned with getting it done.
The whole art of dealing with people is to bring out their best side, but it is frequently the case that by keeping someone waiting you can, in the space of 20 minutes or less, convert someone who arrived, and was enthusiastic and cheerful at the time of arrival, into someone who is resentful and antagonistic by the time you meet them. Only insecure people need to be late to impress upon others how important they are.
If one is going to be avoidably detained, the correct thing is to call, as soon as you are aware you’re going to be late, and let the other party know that the time of meeting must be adjusted, so they can plan accordingly.