It's the angry Scotsman attached to them.
(Kidding, I'm kidding.)
I know a guy who has a chanter (the flute piece that the notes are played on) and they're not that loud. Though they still grate, which is why East Coast rock-and-rollers work them into their songs.
So there must be a resonance thing involved somewhere in the whole octopus. I can't imagine that the kilt has any effect, no matter how much lanolin is rubbed into it.