There are numbers above.
There are 6 million enthusiasts who know bikes well, 12 million bicyclists who ride Walmart bikes from time to time, and 160 million Americans of both sexes who could but never ride bikes.

It seems they are not sold on lightness, carbon, numerous gears, etc and would prefer an inferior but low-hassle and low-maintenance bike. It's the same reason why they prefer automatic cars with the maximum number of cup holders as the first criterion.