Shimano's silent clutch hubs were mostly spec'ed on Police bicycles so they could literally sneak up on a perp without being heard. These bikes are MTBs so that's why the hubs are MTB-types.
That said, all the Shimano road hubs I've used (105, Ultegra, Dura Ace and a couple of sets of Shimano pre-built wheels) are almost completely silent with just Tri-Flow as the lube. My Campy Chorus hub is anything but quiet.