Not surprising, although the tendency seemed surprising to me as well. Until a realized that a good stage/film actor doesn't necessarily have the skill set needed for a good roleplayer. The actor has a script written by somebody else to work from and also gets to practice delivering his lines over and over, in a highly predictable environment. The roleplayer must not only create his own lines, he must do so on the fly and in response to a constantly-evolving situation.