Hope that guy shooting the M10 never shoots a real one! That's just about the number one least recommended way to hold one.
As for why only M11s were made thus far, it's probably due to the knowledge of them. While the general public is more likely to recognize the M10 as its known as an 'evil assault weapon', the M11 has been featured prominently in a number of PC and console games, which makes it a little more in line with the airsoft crowd. Just a guess.
Personally, I'm still waiting on an SWD M11/9. For one, they were produced in much greater total numbers than the M11 or M10, and they're much more popular in the US civilian NFA market. Additionally, the possibilities are endless since so many upper receivers have been mader for them in real life - imagine an airsoft version of the Lage MAX-11 upper receiver, or the SCA Suomi uppers!
Edit: Here's an M11/9 kitted out with Lage stock, grip, and upper receiver with a C-More red dot. This is the kind of customization I'm talking about.http://www.max-11.com/photos/MAX11%20Cover.jpg
By the way, saying MAC-10 or MAC-11 is like saying Colt16 or HK3. It's a MAC M10 or MAC M11 - and rarely even that since most were made by RPB/SWD during the rush years in the 80's! "MAC" by itself is an appropriate abbreviation, however, in much the same way "AK" is a fast way to refer to AK-type weapons in general - even ones that are actually called AIMS or AMD65 or MAK-90.