Why aren't there more helicopter aerobatics at airshows?
First off: I'm not a pilot.

I believe there are two additional issues here:


There is no pilot in the RC helicopter. The forces exerted in some of those maneuvers look pretty extreme, I highly doubt even the most well-trained aerobatics pilot/astronaut/fighter jock would be conscious longer than about 2 minutes into the video you posted. I'm not even sure if they would be able to survive that.
Scale. All sorts of weird things happen when you scale complex systems up or down. (A famous example is the square-cube law: when you scale a structure up linearly, it's area scales as a square, and its volume (and thus weight) scales as a cube. So, an ant that is 100 times bigger will have feet that are 10000 times bigger but will have to support a weight that is 1000000 times bigger.) For example, the airframe of the RC helicopter is much stronger in relation to its size than it is on a real helicopter. Also, RC models (not just helicopters) are typically ridiculously overmotorized compared to their real-life counterparts.