This isn't an accurate view of Amazon's current position in physical ecommerce. They always planned for each unprofitable line to become profitable as it matured.
Amazon's doesn't have many loss leaders in physical ecommerce any more. They used them to build those businesses 10-15 years ago, but they don't need them anymore. The only loss leaders as a category they maintain are digital. And even that is pretty limited to Amazon Video/Studios at this point.
It's a false division - physical v digital. Prime customers get free delivery (physical) + video.
AWS is a genuinely different business, the rest of it is all bundled together. So, they have digital loss leaders. And they may not have many physical loss leaders, but the ongoing argument that they have all these lines which are profitable just doesn't mean anything when customers don't want an online shop for X specific thing. They want an "everything store".
Prime video only exists because of the incremental prime sign-ups, prime renewals, and prime spending money on physical retail. It's all they care about.
Amazon's doesn't have many loss leaders in physical ecommerce any more. They used them to build those businesses 10-15 years ago, but they don't need them anymore. The only loss leaders as a category they maintain are digital. And even that is pretty limited to Amazon Video/Studios at this point.