Why did these British queen consorts . . .?

Well, Queen Adelaide couldn't be known as the Queen Mother, because she didn't have any children. I think Queen Dowager was the correct term. But when Victoria wrote a letter of condolence to her on the death of William IV, she was reminded that it should really be addressed to the Queen Dowager. "I know that" Victoria replied. "But I shall not be the first to remind her of it."