Do you think employers hire people they do not need?
Do you think that having 2 part time 20 hour a week employees is more expensive on payroll than 1 40 hour a week full time employee?
Do you know what happens when a place of business sees increased sales and they're understaffed?
Businesses aren't a charity to their employees -- they hire based on need. If your now understaffed establishment can't handle the new influx of people able to shop there then you're going to bleed anyways as they go to other places for the same items.