Although there are plenty of counter-examples, the point still holds: whistling has come out of fashion, I think, since the 1950s. The same can be said of many other activities that have become too closely associated with that petit-bourgeois lifestyle - regardless of their objective usefulness or quality.

Whistling opens several octaves to unaccompanied music that are not covered by human voices; for this reason alone, musicians should cherish the idea. Furthermore, there are many things a mouth whistler can do that are impossible on a tin whistle or flute.

Those who remember the fifties (and were later attended to by Roger Whittacker and the like) are slowly retiring from the scene; so here's a new chance. Go for it!