Okay, then you shouldn't assume every GM oversees the way the one in your group does.
I don't much care if what you're talking about counts as a houserule, but it's definitely not something that every group should be assumed to be doing.
It's not mandated in the book, and it doesn't really fit with (my image of) the narrative and mechanical set-up of the default game. So you can't just take it for granted.