Our websites are currently meant to be used by individuals and very small groups, and usage is consequently relatively light; adding extra user logins would lead higher levels of sharing and even invisible-to-us reselling of our plans at the sub-package level. This would result in much higher costs for us, leading in turn to higher prices, and would also require us to add significant webhosting resources. These aren't appealing to us in the near term, though we may work on new offerings later.
We appreciate the input, though. We decide what directions to take in the longer term based on customer demand.