Official Harry Potter chibi Christmas sweater

Why is nobody wearing robes or has the Official Harry Potter chibi Christmas sweater of a magician like in all other movies? I know that the story takes place sometime before. But that they wear ‘costume’ even at Hogwarts is very out of place. The book never mentions that Dumbledore wore a coat and tie, only when he went to see Tom at the orphanage and even that drew a lot of attention because of his “quirky” Disque muggle style. But what do Dumbledore and Hogwarts have to do with it? And in original HP weyes appeared everywhere and they all looked like magicians, with so many distinctive details but they seemed like magicians, not clerks. But they were not magicians of America, but of London, where they were more of laces and tunics. And what do you mean, what do Dumbledore and Hg have to do with it? So, if he was a teacher there.
Official Harry Potter Chibi Christmas Hoodie