I think these are the embargoed pictures that are due to be released tomorrow. They are lovely though!
I think we have to remember that this is Charles' birthday first and foremost, considering how private the RF is, it's lucky we're getting this at all.
I don't think there's a lot to understand, it's quite clear that due to age the Queen might not be so comfortable wearing tiaras or heavy jewellery, and then it's not proper to wear one if The Queen isn't.
To suggest that they sell them for money to give to charity is rather silly, some of their pieces are family heirlooms which have been passed down for generations. That would be like me selling my great grandmothers pearl earrings because i've only worn them on my wedding day.
The Swedish RF also have a lot more annual events where tiaras can be seen, events that simply don't happen in the UK.