EXACTLY.
You can't just put on a suit and say it fits because the pants fit you. The cuffs have to be of a certain length when you hold your arms out like Frankenstein or a zombie, not too short but not too long as well. Where they fall with your hands by your side is usually irrelevant as long as they're correct with your arms outstretched. You shouldn't be able to reach above your head comfortably in a jacket...it's not worn for practical use. They are not meant to be buttoned completely; it's not a military uniform. The pants should be worn across the navel and should always be worn with a belt lined up with your gig line, that is, the edge of the belt should be perfectly in line with your shirt and your fly, making one seamless line from your neck to your crotch. If you're wearing a necktie, it shouldn't go any further than the bottom of your belt. A black bow tie is typically frowned upon unless you're trying to look like The Penguin or a waiter, or unless you're in military mess dress...then it's just part of the uniform. The pants should fall just above the top of the bottom of your shoes while standing and your socks should go with either your tie or your shoes (if it's black). Brown shoes are a serious no-no unless you're wearing a grey or blue suit.
It sounds like a bunch of fashion victim bullshit but it couldn't be further from the truth. It's proper dress etiquette, much like how you eat at the table. Napkin in your lap, left hand in your lap, use your knife only to cut each bite you eat, then put down the knife, change hands with the fork, eat, then start the process all over again.
Of course, there are certain etiquettes for different cultures, but this is typical western anglo-saxon etiquette we're talking about.