Not related to boxing so much, but the U.K. military and the U.S. military recruit in different ways, with different expectations. Many or most U.S. enlisted military people volunteer with perhaps previous training in a different career, and thinking of options for other careers after a hitch, or several, or after retirement, so it is a sort of chapter in their lives. My sense is (no expert) that most U.K. military people see this a a lifetime career choice. That's sort of who they are and what they are, and they're all in for life. There are advantages to both cultures. A retiree from the Royal Navy snorted at the mention of the U.S. Navy, which to him likely looked like slackers and misfits.