We're SO SPECIAL- and not just Mil types either...
An inbred arrogance that says "we are so totally different, unique, and yes SPECIAL". I did an MOD office IT installation project 15 years ago and the level of customisation of standard Microsoft products was eye-watering. And it didn't work, was late, and cost a bomb. No doubt experts will be able to argue otherwise. COTS (commercial off the shelf) is a 4 letter word. Civil ATC was as bad, only now they buy COTS and then modify the hell out of it- making it expensive, unreliable (as it doesn't do what it was designed to do) and unsupportable. The same thinking applies across the board. It's a cultural thing...