A customer who leaves a device with you is anxious: their work, studies and photos are on it, so they call every day. A numbered ticket they can check on the site, and a message at every change — diagnosed, awaiting a part, ready — reassures them and saves technician time.
In repair centres lost information costs money: a part fitted but never recorded, a recurring fault nobody remembers fixing, or a promised date that was forgotten. A ticket holding the fault, parts, technician and due date puts all of that in one place.
Companies are the steady income: monthly maintenance contracts for office computers and networks. When each contract tracks its visits and every report gets a ticket, the service looks organised and professional, and contracts renew without you chasing them.