I know, there isn't one, but why not? There's a gaussian and radial blur. What's so different about a motion blur?
I can create a sudo-motion blur by grouping several objects and moving one object off the page, then moving the center of the radial blur to that side, in the radial blur dialog. It would be much easier with a motion blur effect.
Another workaround is to blend 2 objects of different transparencies, but I can't save it as a graphic style. Transform would work, if transparency of "duplicate" objects could be altered. I don't see a way to do that either.
If anyone has some creative solutions for motion blur effect, THAT CAN BE SAVED AS A GRAPHIC STYLE, I'd like to hear about them.