But just because they can doesn't mean they should.
I'll give chain saws more of a pass because they do something almost nothing else can. But leaf blowers ... I wouldn't mind so much if they cut cleanup time significantly, but based on the length of time I hear my neighbor using his, it's not saving him a minute.
However, this is the same guy who has one of those big no-pipe motorcycles. So maybe he simply has a thing for gratuitous noise.