Playing with words again. You're only able to use them because they exist.
With respect, you're either being silly or not reading what I write. Of course I would not be able to use 'low-rated' plug fuses if they didn't exist (either because they weren't manufactured or because I lived somewhere that did not use plug fuses at all). As I said, I
do live in a country which uses plug fuses, but I would
not use anything other than 13A ones if I did not think that there was a potential benefit to be had by using lower-rated ones.
What has that got to do with it?
Everything, I would have said. You said that the issue of plug fuses only arose because of ring finals. In response, I suggested that unfused plugs on a 32A radial probably would not be regarded as acceptable.
I said I can't prove a negative. I have never said there is a positive downside.
I maintain that there is no positive upside ...
If neither of us can think of a positive downside, but I (but not you) think that there is conceivably a positive upside, can you not understand why I feel that one might as well do it (given that it essentially comes with no cost).
... - otherwise (at least some of) the rest of the world would have introduced them.
It may well have been considered 'impractical' in countries which do not have fused plugs, since it would presumably require the installation of multiple 3A circuits, and probably the invention of some new plug/socket to prevent things being plugged into the wrong socket.
Conversely, give us an example of a positive upside of fitting 3A fuses..
I am sure you would already have done so were there one.
I have repeatedly explained what 'potential positive upside' that I see. In the absence of downsides, a 'potential upside' (even if only slight) swings the balance in favour of that approach. It may conceivable occasionally do good, and the 'worst' that can happen is that it provides no benefit.
Think of a person with a serious illness who is offered a choice of two treatments. There is no known downside of either, but one of them might conceivably (but very probably not) offer a slightly greater chance of saving their life. Which would they choose?
Kind Regards, John