Actually CNBlue does handsync, FT Island does as well. and the few other musicians that use live instruments. The biggest problem is the set up and tear down of the equipment necessary to have groups play live that ends up being the major reason why groups handsync. Typically handsync happens when groups are playing on a shared stage with a time limit for the show, whereas if the group has their own stage it is fully live. Its pretty easy to tell when CNBlue does it cause Jonghyun tends to play things a bit differently, I'm Sorry is the best example of it. watch?v=tEmlC4arFX0 is a video where they play live and watch?v=orqC0Hksf-4 is where they hand sync. With the live one, look at how they are corded into the amps and have the footboard switches at the bottom of the mics for added effects.