I do not know the reason scammers are still using this way to scam people. It is like many people are still being victims of this type of phishing attack is my guess.
Because they feel that the scam attack is legitimate, as sent by Trezor, they use this method... If scammers carry out such scams, it is clear that there are still victims.
Why would someone give their wallet backup no matter it's from a legit or fake representative? The backup is to recover our wallet in the case of losing our hardware wallet or any technical malfunction that makes the device non-responsive.
Anyone who wants to keep their crypto safe should keep it to themselves alone; sharing with anyone is simply asking for trouble.
Only we ourselves know the wallet backup; no one else should know, including relatives, let alone representatives from the company.
If someone still believes in such a trick, they are likely foolish for allowing others to access their wallet backup.