Do you ever apologize for being late?

Hi! I see patients on a daily basis. I am always punctual, because being late is a major pet peeve of mine. Most of these patients are always late to their scheduled appts. In addition to calling the day before to remind them of their appts and actually having a heart to heart conversation with them about their tardiness, a good number of patients continue to come in late by 30 minutes or more. The kicker is that they never apologize. So, for those of you who have a habit of being tardy, do you apologize? If no, why not? Is it a power play? Is it just a bad habit? Attention seeking? Time management issue?