It is Monday morning in Lapeer County and the first call of the day is a customer whose problem came back over the weekend. Your best tech has to drive across town for a second visit nobody gets paid for, and the customer is a lot less friendly than they were on Friday.
With a quality program in place, every type of job has a short checklist the crew finishes before they leave, with photos. Every callback gets logged with a cause, and once a month you look at the patterns: which jobs, which parts, which steps.
Callbacks stop being a mystery. You fix the step that keeps failing, coach the person who keeps missing it, and your schedule stops getting eaten by work you already did once.