If the bb faces have paint on them, they ought to be faced, but doesn't seem to be particularly necessary nowadays.

Not once have I had a customer complain about bb noise and upon actually facing a bb with paint on the faces from the factory, found that the faces were even.

I face the ht and bb of every bike I build for myself; any high end build in the shop. OEM bikes could probably use it, but is not a common part our usual bike prep and setup routine with anything other than bare frame builds.