There could be several factors causing this:

We  can only report what data you send us, and often this is the result of  people abandoning the site or identifying themselves on site without  explicitly being asked if they want to receive emails. This would result  in an "unknown" status.

The ecommerce platform may not be set up  correctly - when people are automatically opted in with a pre-ticked  check box. If the system does not pass these people to their subscriber  list, we will not receive their subscriber status, but we will receive  the contact as attached to the order.

Conversely,  if people do not check the box, it may not mean they have explicitly  opted out so their status would still remain as "unkown".