A boutique manager's main job is supervising other employees. But if there is a need, a manager may need to fill in for one of the employees.
I work at a boutique and see this often. If an employee doesn't show up for work, or if there are more customers than usual, my manager has to fill in wherever there may be a need. She might greet the customers or work at the cashier as needed.
So a boutique manager has to know how to run a boutique completely. He or she has to be flexible and adapt to the situation. I admire my manager a lot for these skills.