Check your anglocentrism ;-). If the US and maybe Australia (no idea, haven’t checked) does something, and the UK does something different, you cannot conclude that the UK is somehow the exception to a global rule.
So far, only the US, the UK (where it’s legal) and Germany (where it’s reported to be common) have even been mentioned, and I’ll add Austria, where it’s allowed everywhere except on main streets.
We haven’t taken a sufficient sample to be able to make any statements about the world. And even if we knew about all places in the world, we could then start arguing about how to weight the results. Do we count populations, do we count drivers, or do we count drivers who need to parallel park their car?
No idea about the UK, but here in Austria it’s illegal on main streets within city limits. So, basically, you are allowed to make a three-point turn whenever you’re allowed to park on the other side of the street (except in one-way streets, of course).
I don’t see a good reason why one would allow one and ban the other.
Imagine a low-traffic residential area, with > 95% of spots taken. The next person who wishes to park will come along in five minutes, so it’s not about getting there first. U-turns are impossible because the road is too narrow; three-point turns take a long time, long enough for some other car to actually come along and have to wait for you. You can probably turn comfortably at the next intersection.
So, if you see a spot on the other side, you can either take it, or go at least to the next intersection or around a block to turn around and go back to your spot. So it’ll just take twice as much driving to find a space.
Congratulations - you have just doubled traffic in a residential area in exchange for no gain that I can think of.
In many places, it’s not the “long-term storage” of the private possessions that is a problem, but the short-term storage. That is, people driving to work and people doing their shopping.
My parents used to cycle the block for tens of minutes in order to find a spot for their own car when I was young. Then the city government imposed a 3-hour parking limit in the area, with special permits available for residents, and there has never been a problem with finding a spot since then.
But as a cyclist, I very much want the right to temporarily store my bicycle on public space. It would be pretty much useless otherwise.
So in order to get rid of parked cars, I’d have to argue using “cars are bad” arguments, not using “public space” arguments.