How much time does it take to boil salmon?
It just has to get to 145F for safety, and in boiling water that happens really fast. 5-10 minutes is totally believable. On top of that, fish is really unpleasant when overcooked, so you really want the minimum possible cooking. (For that reason, boiling is not usually a great way to cook fish - you tend to overcook it easily, especially the outside.) Note that this is the conservative, safe temperature, intended to be good even for people with weaker immune systems. Many people prefer it cooked to a lower temperature.

When you cook beef or pork for hours, it's presumably because it's a tough cut with lots of connective tissue to break down so that it's tender enough to eat. For cuts that are pleasant to eat as soon as they're cooked through, there's no reason to cook longer. You wouldn't cook a steak or pork chop for hours, and that's if anything even more true for fish.