People obsess about physical beauty, famously in men judging women's beauty and women judging themselves, seemingly far more than can easily be explained by evolutionary biology, which only cares whether this mate will produce good offspring.
Photographs of models are interesting, because they certainly transmit no pheromones and carry extremely little information about personality, yet they often very strongly induce feelings about attractiveness and attractedness.
The most likely explanation is physical appearance communicates a tremendous amount of information about social class. Decode that information. Class may be extremely important for success of offspring. It is interesting that humans have evolved to be so sensitive to these cues.
In porn, there are often no class cues derivable from clothing, yet people still can and do form very strong opinions about beauty.
A more outlandish explanation is that humans are being puppeteered by their microbiomes, both controlling what a viewer perceives as beautiful and controlling the appearance of the viewed. The bacteria's manipulations are all part of Their Plan.