'horrendous hole'? Do you mean the 10-15 minute walk from Market Street to the Caltrain station?
I'd say adding 20 minutes each way to your commute is a pretty big deal.
Just because you can walk does not mean everyone else should as well. There is nothing wrong with choice, public transport would be a welcome addition to almost every stretch of urban destinations, that does not curtail walking in any way, shape or form.
In short: Walk all you want, just gimme mah ride, is all.
I guess I'm spoiled by the well-interconnected transit systems in many international cities; step off the (high-speed) intercity rail and downstairs into the core of a robust subway system, or walk to the bus terminal next door.
San Francisco once had such an intermodal transit hub in the Transbay Terminal; the city is seeking $2.5 Billion to rebuild it.
Until then, we'll have to rely on private transportation like the 'dollar cabs' described in the article, or San Francisco's very own Lyft and Uber.
I personally bike about a mile to a train station in Palo Alto, and about a mile from Caltrain to the office in San Francisco.
However, San Francisco has some fundamental problems that make it less hospitable to biking than Copenhagen. It is notoriously hilly, and doesn't have the awesome protected bike tracks that Copenhagen has.
I recently ran across a hard-to-believe, but as far as I can tell, accurate statistic: the Copenhagen metropolitan area has more miles of protected bike lanes than the entire United States combined does. That is somewhat surprising, since the Copenhagen metro area isn't really all that big.
Unless they leave you stranded because they are "full" of bikes. Like most non-local trains during rush hour.
Worse is trying to rush the distance catching one of the hourly-only off-peak trains. Or having to carry anything other than a light bag the distance.
If you're 1) rushed (have places to be / people to see / work to do), 2) the weather's poor, 3) you're female (the area's improved but it's still not the best side of town), 4) you're risking a 60+ minute wait if you miss the train, etc., it's not particularly pleasant.
Walking a similar distance along a different or safer route, where I've got the time to wander, or where transit service is such that I've only a few minutes wait (or as is more likely the case on much of Muni in SF: you've simply no idea and the wait may be anywhere from 10 seconds to hours), the situation's not so bad.
But miss your CalTrain connection and you're 30-60 miles from home in a part of town with not much to offer. Though that too is getting somewhat better with the ballpark and revitalization going on.
Some people are limited mobility as well (like the elderly), and/or especially vulnerable to heat and inclement weather.
It's a little offensive to generalize about "Americans" as a whole, especially based on the comments of exactly 1 person, so please don't. 300+ million people live here, with often very different customs and practices, of different social classes, ethnicities, beliefs and worldviews, and living in many different geographies. It's not as diverse as all of Europe, but not even close to homogenous and easily generalized either.