Men's shirts

Sometimes when I am having a cup of coffee and reading while at the Water Gardens, a multi-block office development. I observe the men and their attire. Of course, I look at the women. The observation is that men who ware tailored shirts, 90% of them ware them outside of the pants with the tails showing. I have done something similar for a number of years and for me it so much more practical and comfortable not to have to try to keep the tails tucked in.

Why did it ever start that men wore their shirts in their pants?

This is my speculation on the future: Men will ware their shirts about as in length as long as some women now ware short dresses. Men and women dress has been changing for years. Women more like men and men more like women. I wonder it men will then be able to be as discrete as women. The future may be a challenge.