Ron is, as we have already said, the glue which holds the trio together, but, strangely, always seems rather reluctant to take a larger part in it.
Yes, I know that we have already discussed how he does want a more active role, and does want to do more with himself, and that may be what he wants on the surface, but, deep down, I think Ron is a little too shy. For instance, he never told Harry and Hermione why he didn't like using the name, and maybe that is born of his insecurities - maybe he's afraid they won't listen.