How daft [a question]
Join any armed forces and you've committed your entire existence to the slights of any current political whim. If you were poor & needed a trade, or had no other means to see shores other than the British Isles, it could be for you – no other 'institution' offers such extensive apprenticeships in any trade. There are other aspects too, not to be ignored... like the comradeship which develops over time, opps & experience. Priceless, many would say.
But as a career? why?