There has to be give and take in the process. The store needs to cover shifts according to business requirements. Employees have lives away from work and they need a certain amount of income to pay bills. The goal is to find the place where those needs line up… where the employee gets the hours they need to pay bills and is willing to be available when the business needs hours covered. If it gets too problematic for the employee to get the hours they need they seek another job, if the business cannot cover the shifts they need covered it seeks another employee.
The concept is pretty simple but you can not count on an employee “getting it” without an explanation. These things are best done in advance (upon hiring) and regularly. I want my employees to know that I am committed to providing a work place that respects them and their needs, is a safe and pleasant place to work, possibly is one where they can learn useful things… and in return, I need the requirements of the business met. That includes the obvious like quality work, customer service etc but it also includes being available to work at the times we agreed they would be available with reasonable exceptions.
Speaking of not understanding things… I once had an employee tell me that I was getting rich “making” thousands of dollars a week… referring to sales. No clue. I explained food cost, his paycheck, rent, utilities, advertising, insurance etc all had to covered, Response? “Wow, that’s a lot”