The mysterious disappearance of the wizarding robes

Where are their robes?

It's just occurred to me. The filmmakers have virtually done away with the wearing of robes, so prevalent in the novels, in Part 2 of The Deathly Hallows.

Why?

We see the Hogwarts students in their school robes first as they march into the castle under Headmaster Snape's watchful eye early in the film and then again in the school assembly scene where Harry finally confronts Snape. But, other than those two scenes, the wearing of robes seems to have disappeared completely.

Harry, Hermione and Ron remain in Muggle clothes throughout the entire film, except for Harry's decision to don (someone's) robes to slip into the school assembly scene. The members of the Order, the Death Eaters, everyone else seems content to wear anything other than the traditional garb of witches and wizards as so clearly established in the books.

Now, let's think about this for a moment. J.K. presents to us a wizarding world where the wearing of robes is as natural to the magical people as wearing jeans and tops is to many of us Muggles. Wizards and witches would feel comfortable, normal in robes and would find wearing anything else strange.

Yet, by the eighth film, suddenly they're all taking the first opportunity to dump their robes and put on slacks and sweaters. It doesn't make sense.

Rowling describes very carefully how Harry makes sure to tuck his Invisibility Cloak and his wand away in his robes when he goes into the Forbidden Forest to die at Voldemort's hand in the seventh book. In the movie version of this scene, Harry's in Muggle clothing.

Why? Well, I know why. It's cheaper, it's easier and it helps viewers identify with the good guys in the final battle. They're just like us. The Death Eaters, while not in robes per se, wear strange dark outfits that set them apart. The good guys dress like we, the audience members do.

I get that. But I don't like it. It's a cop out. And it's not right.

One last question: where do all the robes go between the school assembly scene (where all the Hogwarts students are in their robes) and the battle scenes that follow? There's no temporal break between McGonagall's duel with Snape and the Death Eaters' attack on Hogwarts and yet somehow all of the robes disappear.

That must be some closet they've got there in the Great Hall to hold all those robes.