OK Bud!
Gotta keep these civil.
He is very right though that if you are not giving the customer a reason to come in, then they will not show up. The majority of the issues I see is appointments are set out too far.
When an appointment is set out further than 2 days the customer has a less likely chance of coming in. Why? Because we stop following up assuming they will remember they have an appointment and then we call the morning of to confirm and they already made other plans they do not want to skip out on.
Set appointment. Confirm appointment same day you actually set it. Follow-up before appointment to make sure they are all set and have no questions you can answer ahead of time. Send video / text of vehicle desired to show it is there and ready for them. Day of appointment, confirm again and have car up front and ready with a sign on it with their name.
Finally, send picture of the car pulled up and ready with their name on it. Customer will show more often than not. If you do this and customers are still not showing up, then there is more going on than is being mentioned.