I think she loves William, the lifestyle and privileges, so she can have that country stay at home wife/mum thing going on. Unfortunately the public pay for it. I would want some return on that social contract! No problem being a stay at home mum - I am!!! - but when you've got public duties to uphold you should do both. So many women juggle 40 hour work weeks and parenting, why can't they do a few engagements per week? You can still be totally present for your kids. During the school day I do lots of home things, look after my elderly mum and take her to her many appointments and such, and have free time to myself to exercise or play video games... or hang out here on Tattle!!!
I'm not an introvert but it sounds really a life full of not so great trade offs for a wonderful lifestyle. I'd put up and shut up and do anything asked of me to live that life though!