Because they have determined that the time of those employees is worth more than minimum wage.

Because they understand that the minimum wage workforce comes with a revolving door — that those employees might only last a year, or less, before they move on to a different minimum wage job, and the jobs for which they’re willing to pay more than minimum wage are jobs which require more long-term employees.

In short, because market forces are dictating that those employees should be better compensated for their time.

I have no problem with allowing market forces to control certain aspects of employment and the setting of wages, so long as everyone is being fairly compensated.