Yes, is it a good question, no? ;-)
There are many (and many!) microstock websites, but how many sell video footage? I only know three of them!
It's a really less offer for customers... and for contributors! Personnally, I make some little "real" video footages with my Nikon and some "basic" digital footages (computer calculated).
And now, it's easier for lots of contributors, because 90% of the SLR camera can make video footage.
I think, it's really strange that Dreamstime doesn't offer footage to sale..
I can't sell it here, but when I sell one footage, commission are really higher than an image!