Clearly they believe that shoplifters still provide net-positive value to them.

Which is obviously bs, just because they don't stop you from doing it doesn't make it a net positive from them. It could just as likely mean that the time and effort to stop it is more expensive than the losses they would incur.

They are offering you a service with two options to pay for the service. Either by watching ads or paying a subscription. You are choosing to consume the content without paying.