AZERTY-style keyboard layouts in France and Belgium have a dedicated key for typing the Greek small letter mu (μ). While not having a dedicated (μ) key, keyboards in Germany, Denmark, Finland, Iceland, Norway, and Sweden provide a means to enter (μ) using composite gestures. Why is this one lowercase Greek letter so significant?
By contrast, the keyboards in Spain, Portugal, Italy, UK, and Ireland do not have a (μ). Why is this one Greek letter so important to French, German, and Nordics? How is it considered part of a standard user experience? Why not the Greek letter pi (π) or some other letter altogether?
And why do the Italians, who are geographically closer to the Greeks than the French, not have that letter?
For easy reference, Wikipedia's article that compares keyboard layouts is here.
While IE and Chrome produce some form of numeric key code, allowing to identify which key the user pressed, in Firefox this is "undefined" (it isn't even a numeric value). I find it hard to accept that the presence of such a key on these keyboards should not be questioned - if there were only 105 keys on a keyboard and a whole group of countries decide to standardize THE GREEK LETTER MU as one of them, there has to be a reason for that. There should be a good reason for that, and I'd like to know what that is.
If I need to write code to especially cater to these keys that Firefox refuses to identify, it will be at a certain cost. If I ignore the keys in keydown but handle them only in keypress there is also a potential inconvenience to my users in France, Germany, and the Nordic countries due to reduced functionality. Knowing why this region standardized on this one letter (even if there are only historical reasons) would help me to weigh these costs.