Low cut shirts, short skirts, etc, it's not really about getting attention(or rather, not always is more accurate), but to enhance attractiveness for its own sake. Almost everyone does that by wearing things they think look good on them, caring for their hair...you know, most people wouldn't go out looking like slobs.
Like jocks who wear sleeveless shirts to expose their strong arms, or Lenny Kravitz wearing tight pants so everyone knows he got a big ***; for women breasts and legs are those things to expose to enhance attractiveness(pending comfort with they're own body --a chubby girl might show off breasts much more than legs for example), there is also a similar thoughtline behind the use of makeup, although with some difference.
So what I'm trying to say is that a person doesn't necessarily put emphasis on their attractive bits to get the looks from others(though obviously it could be the case), but because she herself knows those are good points of her body and this gives confidence about her appearance. If you're confident you're more comfortable around people.
That being said, one advantage we got over men is that we can undress much more than you do when it's hot by reducing the size of the clothing, so that's a very strong reason for not wearing any pants in summer.