Because there are no (or way too many) typical pattern. Everyone is writing them different. And those pattern are always garbage only, not needed for anything. So why on earth should we slow down the import process that much especially as there is an easy fix for this available? RegEx is time consuming especially on weak systems so you better don't use it if not really needed...Why can't the Importer RegEx those typical pattern out?
Aside this, if you are using local metadata (as suggested) you can name your videos completely as you like... Even "MyMovie #001.avi. MyMovie #002.mp4,... " is working then.