This would be very useful as it will protect the business and prevent service providers from stealing clients (contacting them directly through phone/email). Most booking systems have this option to restrict certain users/groups of users and that's one of the reasons as we are considering switching to another system

I completely agree that there should be user specific restrictions to access any client's information. Just their name and service booked is what is needed

It's necessary to protect client's personal data and company's assets to prevent data breach.