A single shared login works fine for a one person business. The moment a second or third person needs access, whether that's a manager, a front desk team, or a partner running a different location, role based access stops being a nice to have and becomes the only sane way to manage it.
Why one login for everyone stops working
Shared logins make it impossible to know who actually did what, and they hand every user full access to billing, security settings, and every location, regardless of whether they need it. As soon as more than one person is genuinely involved in the day to day, separate accounts with appropriate access become worth setting up properly.
The three roles, and what each one can do
Owner is the account holder, with full access to everything including billing and the ability to remove other team members. Admin can manage most of the day to day, sending requests, viewing feedback, managing locations, without touching billing or being able to remove the owner. Member is the most limited role, suited to anyone who needs to send requests and see feedback but should not be changing account level settings.
Who should be an admin vs a member
A manager running a location, or a partner with genuine shared responsibility for the business, fits an admin role well. Front line staff who need to send the occasional review request, or check recent feedback, but do not need to touch settings, fit a member role. The general rule is to give the access someone actually needs day to day, not the most access available by default.
Inviting someone without handing over the whole account
Adding a team member is a simple invite by email, with the role chosen at the point of invitation and changeable later if responsibilities shift. Removing someone, when a staff member leaves, takes the same few seconds and immediately cuts off their access, without needing to change a shared password that everyone else was also using.