That's a perfectly valid way to view the world and the relationship between it and the player characters. However, i don't particularly like that view. It makes the PCs special just for being PCs. There's no reason a town guard couldn't gain a level after helping defend from the orc attack. After all, that's a perfectly valid player character backstory.
This is actually related to the overall idea of behavioral realism: plot armor, special status and relative power level are all things that contribute to players not taking their characters' place in the world seriously or realistically. As such they don't worry about mundane stuff like being tired, hungry or dirty.
I'm not saying PCs aren't special. They are the protagonists, so the things that happen in the game necessarily center on them. But they aren't, in my view, categorically different than the other characters and creatures that inhabit the world. They are different by deed.