The problem is that contracts don’t bind subsequent recipients, copyright does

Google gives the model to X who gives it to Y who gives it to Z. X has a contract with Google, so Google can sue X for breach of contract if they violate its terms. But do Y and Z have such a contract? Probably not. Of course, Google can put language in their contract with X to try to make it bind Y and Z too, but is that language going to be legally effective? More often than not, no. The language may enable Google to successfully sue X over Y and Z’s behaviour, but not successfully sue Y and Z directly. Whereas, with copyright, Y and Z are directly liable for violations just as X is