If you want to have your customers not register as a joomla user but just in HikaShop you can use the "registration" option under the tab checkout of the configuration of HikaShop for that.
Other than that, users in HikaShop are normal joomla users which can be in different joomla user groups (propects, customers, suppliers, employees for example). But that has nothing to do with HikaShop, it's handled by Joomla. So I don't understand the point you're trying to make.
If you have more information on your issue, you can post a message on our forum and we will look at it.