Lovely video. I really hope it heralds the start of her coming back to public life in good health, not something altogether sadder as suggested.
Why do it? Clearly people have short memories of the February and March frenzy. I think they were ticking off all the conspiracy theories. About her being dead, at death's door, a stand in, her marriage being over and that she's actually left William, that the children are in distress etc, etc. Hand on the gear stick? Showing her ring finger so the twats get a clear view, nothing being "hidden". It won't stop them, but then nothing will - certainly an arid statement would not, so why not go all out with a gorgeous video. Good for Catherine and William for going for it.