Minor celebrities, especially female, dress to impress. Specifically, they hope that some unusual and daring costume, possibly with an apparently inadvertent flash of body parts, will get them covered in the media, which refer to these flashes as "wardrobe malfunctions". This term was coined after a Superbowl appearance by Janet Jackson in 2004.
Before her marriage to Prince Charles, Lady Diana Spencer was photographed in a long skirt with the sun behind her, so that her legs were visible through the fabric. She was not thought to have planned this. But if a celebrity poses for a similar photo today in the thinnest of materials, we may assume she knows what she is doing. (Later in her career, the Princess of Wales was thought to have become much more conscious of her image.)
Women, however famous, have a perfect right to go about their normal
business without some nosy journalist commenting on the visibility or lack of
underwear or their physical condition (weight, cellulite, pregnancy, etc.). But when they attend a publicity event in the hope and expectation of being photographed, and then pose glamorously for the cameras, then surely their appearance is self-consciously planned, and they (or their publicists) are colluding with the salacity of the gutter press. This must be especially true for those women whose celebrity is based on image rather than substance.
If the function of the dress is to titillate the public, then a true malfunction only occurs when the dress fails to achieves its proper function - in other words, when the body parts remain decently concealed. (Even when the dress actually comes apart at the seams, some observers may imagine this to have been engineered, and the flustered embarrassment to have been rehearsed.)
Meanwhile, with characteristic hypocrisy, the tabloid press pretends to be shocked by the more gratuitous flashes, and refers prudishly to the person's "modesty". As if.