Being on time was always a huge thing in our home and a value I carried into work. BECAUSE, as we were told so often, it shows that you value the other person's time and it's a matter of respect.
Had a military (Marine) lifer uncle who, when we went to visit him in D.C., we quickly learned meant be ready 15 minutes early and be IN the car at the time mandated....not just walking towards the car, or getting ready to open the door...nope! Be IN THE CAR or you will be left standing on the driveway alone.