No one is "ignoring" the fact Camilla is also Princess of Wales. As with any woman who marries the heir to the throne, she enjoys all of the titles and styles traditionally granted or automatically succeeded to by her husband. For obvious reasons, she has chosen to be styled as Duchess of Cornwall, but her married title and rank if Charles had no other titles is "HRH The Princess Charles". She is still a princess of the UK by marriage regardless of which peerage she is styled by.
Louise is a similar situation. By right of the 1917 Letters Patent, she is automatically HRH Princess Louise of Wessex as a male-line grandaughter of The Queen. At her parents' request, she is currently styled as the daughter of an Earl, which is fine because she IS the daughter of an Earl. Assuming the current letters patent remain in force, she can assume her superior rank and title at any time in the future.
Once Charles becomes King, these situations no longer can be applied because we are now dealing with a very different scenario. As the wife of The King, Camilla assumes automatically the title and precedence of HM The Queen in her own right. If her husband dies five minutes after his mother, she is HM Queen Camilla for the rest of her life as a dowager queen. Only Parliament can take away her rank and title as the wife of the King.
Being "HRH The Princess Consort" means she is a princess of the UK in her own right like Prince Philip is. But how can this be when she is already Queen? It can't without legislation being passed by Parliament taking away her superior rank and title, leaving The Sovereign free to create a lesser one in its place.
She cannot be "styled" as a princess of the UK when she is legally Queen Consort and holds superior precedence and title.