You're certainly welcome to purchase any of the white-label services on your own Workify site.
One reason you might want to do this is to help market your Workify site. To purchase a service yourself, you will need to purchase on your marketplace link - not through your dashboard when signed in as the owner. You'll then have two accounts: one where you sign into workify.co as the owner, two where you sign into your marketplace link as a customer.