I'll be the first to admit that I never got into the "selfie" thing.  I could never understand why some people were so self obsessed that they had to post pictures of themselves ALL THE TIME doing even the most mundane things.  And more than that, why all the emphasis on trying to look "sexy" in many of those selfies?
In fact, there is a special category of selfies that the Urban Dictionary defines as "thirst Traps".  Thirst Trap  - A sexy photograph or flirty message posted on social media for the intent of causing others to publicly profess their attraction.
Now we know it happens -- at least some of the time. Wait for it....Income Inequality!

The Daily Mail  reports that University of New South Wales researchers analyzed thousands of selfies posted to Instagram and Twitter from people in 113 countries. They found women who live in environments with greater economic inequality were the most likely to sexualize themselves in images.

(could it be "bait" to attract a path to a better life..i.e. a Richer Guy?)

The pattern held even when researchers controlled for other factors like population size, human development, and internet access.

Study authors conclude that sexy selfies are a marker of social climbing among women that tracks economic incentives in the local environment.  In other words, in today's environment, looking sexy can generate large returns, economically, socially, and personally.