And why not? Heroes are usually depicted as being well built, clean, and not only do they still have all their teeth, those same teeth generally are in mint condition. How do they do it? The normal hero wears the same sort of leather garment day-in, day-out and, apart from a sword, usually doesn't carry much in the way of a razor. He doesn't have a toothbrush (let alone floss), at night sleeps on the ground, outdoors, and during the day either fights or rides or trecks through the jungle - activities that have a tendency to make their pursuers work up quite a sweat. Still, you never hear of a hero taking a bath - and even so they look smashing, have a smile normal people have to spend a fortune to achieve it and obviously don't smell despite the fact that the word soap does not seem to belong to their vocabulary.

Perhaps it's genetic. Like that astounding ability to master any craft within seconds, if it takes that long.
Just look at the young hero, who, after years and years at the whinch, breaks free, grabs the surprised guard's sword and wields it like a kung-fu fighter after twenty years of seclusion in the right monastery.
Then, when he flees the scene after the fellow rebels have all been slaughtered, he jumps on a horse, picking the best one as if by accident and rides off in a gallop, clearing the perimeter defences in a jump that would land even experienced fox hunters in the dirt. And it doesn't stop there. Henceforth he knows how to hunt, how to treat minor injuries (of others, heroes never, ever get hurt) and how to kill magical beasts.

Most of all heroes know how to treat the fair maidens they routinely rescue. Around them they are courteous, patient and have exceedingly good manners. They never fart, burp or rearrange their private parts. And all this despite their lack of formal education and the fact that they have never been to dancing class, let alone been introduced into society.

Also heroes never seem to succumb to jealousy when they learn that the damsel in question is already engaged. Not that a hero would ever ask for the hand of one of the ladies he has rescued, though. They are far too independent, work too long hours and, after years and years in slavery, are probably not too keen on matrimony anyway.
Instead they engage on long and dangerous quests, do manly deeds and only occasionally bonk the local witch (usually under the guise of being enchanted and/or that "it's necessary for the magic to work"). It's a demanding life, a life that would take its toll on the strongest of us, making us age prematurely, and, finally, die when at last we meet a foe who's stronger than us.

Not so heroes. Heroes don't meet adverseries who are of superior strength to them. And heroes don't die. Mere people may die heroic deaths but not heroes. They just sort of vanish. One moment they are there, doing what they've done all their lives, and then, suddenly, the stories telling about their heroic attempts to save mankind from universal evil stop. No-one ever told how the hero died. Or gave up and retired to an old peoples home, shouting at the young nurses.

It's probably a conspiracy.