Who the Hell Loves Teeth?

Can anyone (perhaps a dentist) explain why dentists say things like, 'I am now going to shove this bloody great needle into the root of your left number 7', 'Just relax, Mr Smith... you're not relaxing, Mr Smith...', 'The large object approaching the pulsating mass that was once your third molar is a 5-gauge drill, which spins at 4,000 revs per minute and whines in that horrible fashion not for technical reasons but because we are sadists', (the last bit they don't say out loud, of course)? Wouldn't it be better if they just shut up? And above all, why do they say it won't hurt?