Why don't we need to blouse ACU pants?

Umm... Who told you that you didn't? I only got out of the Army a few years ago, but we were still required to blouse our ACU trousers. The only times that we got away with not blousing them were during specific heat cat levels, some training exercises, and on deployment. Maybe things have changed...

The only ACU pants that I have seen correctly worn not bloused are the flight suit variation, and that is due to functionality of the material. Other than that, all other ACU/ABU combinations are required to be bloused over the boot, or tucked to give a bloused appearance.

What are your duties in the Air Force, and what does your command specify? Some duty position having bloused boots interfered with the rapid donning of required protective apparel. Those in the Base Fire Department may be wearing protective foot wear which are not laced, and resemble something more of a Wellington style Safety Boot.