There's no such thing as the average or normal foot.....the vast majority (around 70%) of people in the United States have been born with or acquired pes planus deformities (flat footed). But in that category you have flexible flat feet, which don't usually require support. And you have rigid pes planus, that do usually require bracing.

You also have to account for age. You for one may not require support right now, but as you age you will acquire arthritis, loss of beneficial range of motion , and probably an excessive range of motion in the medial to lateral plane, allowing for over pronation.

You're claim may be closer to correct if you specified age, weight, and activity level, or specific a foot type.

It is in fact exceedingly rare to see western people who can remain in perfect subtalar neutral while weight bearing, and thus it's fairly rare for people to be active to a late age without sustaining chronic foot and ankle injuries over time.