Empress Merel, in the US, there would be tax issues, and I suspect there might be in the UK as well. For example, First Ladies are not permitted to accept clothes and other gifts from designers without paying taxes on them. Nancy Reagan got into trouble for this back in the 80's. I might also point out that when Michelle Obama recently wore an Alexander McQueen dress, she was criticized because it wasn't of American origin. Some people really do care very seriously about this sort of thing, and since the British royals are constantly being subjected to much criticism involving the cost of the monarchy and how much they do or don't do to earn their privileges, it behooves the female members of the family to be very attentive to the importance of promoting British designers.