I think that Vulcans think that saying "please" etc is a waste of time.

Except Amanda agrees that Sarek is ordering her around, not just that he's not saying please. I don't think there's any way out of the horror of these gender relationships, especially with all the kneeling and the general attitude Sarek has towards her. *sadface*

...This doesn't exactly absolve either of them of being jerks to Spock.

Which is of course their worst crime, because HOW CAN YOU BE MEAN TO HIM? HE IS SO AWESOME.