@Paul Farquhar is right about monsters.
If the general population encountered monsters at even a 10th of the rate that PCs encounter them, civilization would never have been able to get started. Humans, elves, halflings, etc. would be extinct, eaten millennia ago.
If the PC encountered monsters at the same rate as the general population, the game would be boring beyond belief for a lot of us and would likely have failed.
The PCs being fated, tested by the gods, cursed to encounter monsters, etc. explains the disparity.
Some settings do things differently as you note, but they still don't have monsters commonly encountered by the populace, or else those monsters are not hostile to civilization(Al Qadim's genies).