I guess I should clarify on what I posted.

A dentist will NOT be pulling my wife's teeth - they will be done at
an oral surgeon's office.  She will be under general anesthetic and
all 4 will be pulled at once (they are all severely impacted).  This
is how mine were done, my mom's, my dad's, my sisters, and basically
all of my friends, so apparently it's not too uncommon here.

The office here in the US said the reason they do 4 at once is that
they don't want to put the patient under general anesthetic more than
once if they can help it - it is too hard on the body.  They said the
most visits they would do is 2, but this particular office would not
do that unless there was a very good reason - they want to minimize
the risk of putting people under more than once.

My gathering from this disucssion is that in Japan it's a little
economics and a little bit "patient care" to spread the extractions
over a few days.  I also understand that the typical Japanese person,
like my wife, would simply say "sho ga nai" when they would tell her
it's going to take 4 visits to pull all of them.

Thanks for all of your replies.  It's been very interesting reading.

Paul