A hairdresser described it to me exactly: between two clients she has eight minutes, her phone shows fourteen unread messages, and she knows three of them are bookings she has to memorise, because right now there is nowhere to write them down.
Why it beats a system at first
A DM has no barrier. The client is on Instagram anyway, sees your work, types two sentences. It is personal and familiar and requires no account. At ten clients a week any booking system is pure overhead, and anyone telling you otherwise is selling something.
Where it breaks
History disappears. A message slips under twenty others and you cannot tell whether you replied. Two clients get the same slot because you answered one in the morning and the other at night. You reply at ten in the evening because otherwise it will not be done by morning. And if you fall ill, nobody else can reach those bookings at all.
That last one is usually the moment it stops being about convenience. Bookings that exist only in your phone mean the salon cannot run a single day without you.
Moving without losing clients
The worst thing you can do is announce that from Monday bookings only happen through a link. Some clients read that as being pushed away.
What works better: keep both for the first month. Put the link in your bio and in your auto-reply, but keep answering messages normally. For regulars, make the first booking for them and let the confirmation arrive in their inbox. Next time most of them will do it themselves.
And expect some to keep messaging forever. That is fine. The point is not that everyone uses the system. The point is that those eight minutes between clients stop being about decoding unread messages.