I also am no longer tucking in my shirts...(wink, wink)
Four decades ago, almost no gentleman or even teenage boy would go outdoors without tucking his shirt in. Whether you were wearing a suit, or t-shirt and shorts, the shirt was tucked. Even the "sweathogs" in Welcome Back Kotter and the Brady Bunch kids were tucked in.
These days, I tuck in for formal situations, including church, but otherwise I go untucked. The more people there are without their shirts tucked, the less others know about what they may or may not have under those shirt tails.
I used to think malls were a target but with all the folks with concealed carry I'm not sure they are.
Remember - the San Bernardino jihadist had pictures of high schools on his phone. Much softer target.
p.s. I still won't go to any mall though and I'm glad I'm not a school teacher.