And they'd be cancelling the order why exactly? Car dealers would be out of business if they weren't allowed to sell stock before they had it for example...
They might not want to develop a reputation of being a purveyor to scalpers in the way that nvidia did.
You seem to feel that scalping is perfectly reasonable business. And sure, it is legal... for now! The reality is that scalping undermines market efficiency. In other sectors, where scalping was more prevalent, it is no longer legal and for good reason.