Doesn’t make any sense to me either, particularly with CDs, where at sites like this you can usually sample the music before you buy the physical product to find out if it’s to your taste.
Pre-internet, there was that awkward experience where you occasionally bought a new release from an artist you’d liked, expecting more of the same, only to find the self-indulgent singer had demanded full artistic control from their record label on the back of some earlier commercial success, turned all leftfield in a desperate need to do something different, and produced their own ‘avant garde’ album, one so different and uninspiring that it turned off half their fans and any singles crashed out of the charts.
Buyers were stuck with such unlistenable rubbish once they’d opened it, shops would not take them back, and all this with prices then at up to £15 a disc. You soon learned to listen out for new material on the radio first.
Someone opening sealed discs will devalue them by up to 50%, just so they can get free lossless audio, or burn mp3s. It’s no skin off Amazon’s nose to loan out FBA stock though.