Stamper,
My reasons for suggesting one crops in-camera are simple: it focusses the photographer's own mind/vision prior to going 'click!', a process that can become blindingly fast with practice, and also, importantly, teaches him to make the best of the available real estate at his disposal. All that film or film format has to do with it is that learning with a small format teaches the value of not wasting space, and if you use film, the cost makes you concentrate more than does a card, which once you've bought it, is essentially a no pain no gain option.
But as I seem to remember, you grew up with film, so why do I feel any need to tell you what you must already know?
;-)
Rob C