In fact, that`s more of a flavor reason. Hobbits pretty much evaded stuff all around in the beggining of movie 1. In movie 2, they still evaded quite a few things, although only Pippin and Merry did so, which is why the cancelling is fairly limited to them. In King Block, they were all tossed into the fire of action, so they didn`t get to evade stuff at all, they all had to "fight" at some point (be it real battles or internal ones).