Why do you think so? William isn't sharing that much and he's the future direct heir. Why should his wife put herself forward more than he does? I do think the BRF is dealing with a surfeit of heirs right now and are handling it in the best way. JMO.
Also, Catherine may not actually be suited for that kind of role. If it came naturally, maybe. Sophie Wessex was in PR; Doña Letizia was a news anchor; CP Mary was in advertising; Maxima was in finance and teaching - all professions requiring a natural interest and inclination for interaction with a public. It's possible some expect too much of Catherine whose background is far more sedate and circumspect. I'm not convinced that such should be an expectation of William's wife as a matter of course, at least not yet.
What would she say? She hasn't the experience to have any real sense of these things yet. Maybe in a decade or so? Perhaps, if she does her homework, but for her to comment now could sound pretentious.
Let her raise her family. Out of that will come experience from which she may naturally rise with interests to which she can speak in a genuine way. There's plenty of time. IMO.