Why does Werkstatt want chassis number to create an offer?

Hi, I wanted an offer by email from a workshop, I indicated the brand Model Km-Stand year of construction of the vehicle, and of course which component it is. But the workshop wants the key number / chassis number or a photo of the vehicle license. Why does it need the one for an offer? At the most it is enough to send the codes 2.1 and 2.2 from the vehicle license, or ?