Isn’t that risky - what if you suddenly have to travel with business and there’s a delay getting a passport?
I’d recommend planning ahead instead, but in my case I couldn’t give up my soon-to-expire passport as I was traveling and didn’t expect another international trip so soon after expiration (to use the alternate means of proving citizenship and identity rather than returning the old passport book).
I assumed Americans would want the same kind of basic freedom to move between countries?
You'd get a really funny look if you were suddenly asked to go on a business trip to the US and you said you didn't have a passport yet. Not sure why it wouldn't be the same if you were in the US and asked to go on a business trip to the UK.
I think the difference is the size of the US. I've traveled a fair bit for work, but never been asked to leave the country. Jobs that do require international travel often explicitly say so in the description and say you must have a passport.
As far as freedom to travel, unless you happen to be on the northern or southern border, you can't just hop on a plane and travel out of country on a whim. It's just flat-out not as easy to travel to other countries here as it is in Europe.
If you're in the US, going to a different country is a major undertaking unless you happen to live near the Canadian or Mexican border, regardless of whether you have a passport or not. Casual international travel is just not a thing for most people.
How come it’s seen as pretty normal to go for example from the UK to New York for a weekend, even a middle class couple might do a Christmas shopping weekend like that once a year, but the opposite, the same distance and cost, is seen as a major undertaking?
I think the short answer is that the US is physically huge. Just the state I live in alone is about the same land area as Germany, and there are 49 others -- many of which are larger than mine.
Just getting to an airport that you can take an international flight to the UK from can be a big deal all by itself. It's not cheap (an oddity about plane fares in the US is that domestic travel can cost as much or more than flying across the Atlantic), and can take a day or two. The cost of the flight from, say, New York to London is not necessarily the major portion of the travel expense.
The travel time is significant, as I mentioned. For a lot of people (pretty much anyone who doesn't live in the general north-eastern portion of the US), a "weekend trip" would require 4-6 days. Vacation time is limited, so not everyone is willing to spend a significant portion of it on an airplane or in airports.
Cost is a big deal -- traveling overseas is expensive, and the prices for things in the UK are quite high as well (probably on par with New York, but New York is very expensive). Most people who aren't wealthy (which is the vast majority of people) could really only expect to afford it once or twice in a lifetime, unless they are willing to sacrifice a lot of other things to make it happen more frequently -- and some people do, but most people have other priorities for the money.
(I wonder why your comments keep getting downvoted? That's weird.)