In my city, the school buses only pick up kids that live more than 1 mile from the school. I live in a pretty dense (albeit still single-family) neighborhood, so almost everybody who goes to my kid's school lives too close to ride the bus.

It's amazing how the majority of the parents are apparently willing to spend five or ten minutes clearing the frost off their car windshield only to drive half a mile and then wait another ten or fifteen minutes in line at the car drop-off, when my entire round trip by bike is maybe ten minutes total.

Frankly, the "large portion of people" in my anecdote are just flat-out doing it wrong, to both society's and their own detriment.

The number of people who do have alternatives are a lot higher than many of them are willing to admit.

Yeah people will use bikes or public transit if it's a better option for them than driving. But decades of carmaker lobbying, terrible zoning laws and bad urban design makes driving the only available option for most Americans.
Cities who invest in good public transit and sensible urban design always see a huge decrease in car traffic.