Sadly, the lighter the fabric and the bigger the bum do not make good bed mates. As is seen sooo often on the larger size models, tunics, tops, cardis etc made of lightweight fabric, tend to 'sit' on the backside thus accentuating the enormity of the backside - so not a good look. The backstage 'stylists' obviously haven't a clue when dressing the larger models, with dresses that 'pull' around the bust or hips; and if there is a need to hide backside and tummies, then only fabric with some weight will do the job and hang in a flattering way.
(I wonder how many of those awful and see through knitted waterfall cardis have ended up in a charity shop !!! )
Of course the guests and presenters are on air to sell as many pieces as possible, so they are hardly like to say that Joy looks a dogs dinner in her thigh crushing leggings and too tight top.