That may be what you believe, but that is not what is happening. The Featured Offer (Buy Box) is not a right or a given. It is like the old Clairol TV commercial used to say, "Only your hairdresser knows for sure". Now just replace the hairdresser with Amazon. It is run by an Algorithm Bot that giveth and taketh away.

In addition, Amazon uses this as a ploy to entice sellers to use FBA but remember this. There can only be one Featured Offer for each unique product. Sellers seem to enjoy it when they have it and then complain when they do not. However, when a seller is disappointed with the loss of the featured offer, they seem to forget, another seller is happy with that loss, because it is their gain.