Calendly is fine for solo consultants. Square is fine for one chair. But the moment you have multiple service types, multiple staff, multiple locations, deposit logic, package memberships, or anything more nuanced than 30-minute slots, you're hacking around the tool instead of using it.
And every hack costs you. Missed appointments. Double bookings. Confused customers. Staff filling in gaps the software should be closing.
The traditional answer is to buy a vertical-specific platform that costs 4-figures a month, locks your data, and still doesn't do exactly what you need.