I thought 411A had been resurrected when I saw his contribution to this thread
then I noticed it was in February of 2011..
Anyway he was right then and still is, many pilots slow down for the slightest of bumps and by such a small amount it wouldn't make a difference anyway. I think it's mostly nervousness and a lack of understanding of basic aerodynamics. Normal speed should be flown unless you hit severe turbulence.