I always carry a whistle, because, well just because I was told to in the scouts. I have never used said article.
On chatting to some folks on a hike recently they stated they wouldn't recognise the sound of a distress call on a whistle.
You know what I'm not sure I would either, given the background noise and just general lack of awareness on my behalf, I am a total daydreamer when walking. (Heaven knows the extra miles I've walked past turnings which on trekking back were clearly obvious
)
So given that I now carry a mobile phone and a GPS to give exact positions to anyone if I was in distress, do I really need to carry a whistle? I probably will continue to do so because they are so insignificant weight wise, and I wouldn't like it to come up in a coroners court that I didn't have one and have people on this or other like forums criticising my stupidity.
So the only reason I see for one is my fear of criticism rather than feeling them to be helpful.