They tap your pin
They see your reviews and your number. It's after hours. They think "I'll call tomorrow." Tomorrow they're busy, or they find the next shop down that does let them book now. You never knew they existed.
They tap your pin → Book online
They see your services and your open slots. They pick Saturday at 11, pop in their name, and they're booked. You wake up to a confirmed appointment you'd otherwise have lost.