I know they want to help mankind with their oral hygiene advice, gently chide those who smoke too many fags/drink too much coke, and frighten little children improve the nations dental health...
...but who wants to go poking about in peoples' mouths??
And possibly cause pain to them?
Maybe they get a secret thrill out of their scary reputation, and like the look of horror on peoples' faces when they're introduced as 'Vladimir the DENTIST mwahahaha' at cocktail parties.
(Can you tell I've got my check up in a couple of weeks?
)