I think it's a lot to do with how anyone is raised and that includes those from the royal family. Lets not forget how Andrew insisted on having private detectives for B&E. I can't help contrasting those two with Lady Louise Windsor, who allegedly got a minimum wage job at a local garden centre, whilst she was doing A levels (good for her) and was recently photographed, presumably coming home from university sitting on the floor of a very crowded train.
I think it's fair to say that because the Princesses, and that was a mistake conferring the Princess title on them in the first place, have been massively cossetted throughout their lives they have very little touch with reality. That came across in a couple of interviews I read with them, one where they stated they were "just a couple of ordinary hard working girls" no you're not! and one of them had dyslexia at school and she viewed it along the lines of some sort of blessing in disguise, I think Camilla Long in The ST, who admittedly is no royalist, wrote rather scornfully, maybe if she'd had attended a school in the cash strapped state sector she might have a different pov on that. They've been parented by a couple of ridiculously entitled profligate free loaders, so of course, like anyone else they've been shaped by an over -indulged upbringing I've actually got a friend who cossetted her child in the most ridiculous way, driving her to school until she was 18, because somewhere along the line that daughter deemed getting on buses was beneath her, my children and their peer group were negotiating the way round parts of Greater and inner London from about 12ish on buses. I just think bringing offspring up to believe they're ultra special hinders development in becoming their own person. I can quite believe B&E because of the gilded cage and their privileged but controlled lifestyle wouldn't have the nous and independent thought that possibly many of their contemporaries would have at their age and just accepted the circumstances they found themselves in when wheeled out by their parents.