I don't know what the source of this convention is, but this is why I was taught that the version "1.2.3" should be read aloud as "one dot two dot three" instead of "one point two point three". The idea is that people--where I'm from at least--tend to read decimals as "point" and not "dot".
Yes, sadly the proliferation of the "two point oh" meme has set society back on that front. (Had we the opportunity to start over, I would have proposed different punctuation for the delimiter to avoid natural confusion with decimals.)
