I actually think a lot of this has to do with location.
For example, Los Angeles, where I live.. The entire "going out" crowd wardrobe is entirely based on the idea of casual, untucked clothing.
- I have an army of cool belts and can't remember the last time I ever got to highlight..
Also, the front tuck, back out look is quite common too.
Though I also remember spending time in the midwest where I saw people tuck shirts into outfits that, let's just say, could have used some untucking.
I do kind of miss the days when I could tuck a dress shirt into my jeans, rock a cool belt and never think twice..
But I can't tell you how many girls, when asked, "In or out?" ALWAYS say, "Wear it out!!!"
- At least around here...