Because the legal system around backpacks are better understood. The more common something is the less legal paperwork there is. Judges understand backpacks and have for hundreds of years. Many judges don't understand technology. As a result when selling a backpack you can rely on the court's understanding and thus not have to account for every possibility. Meanwhile because the court might not understand technology you have to account for every possible trivial thing.
Pretty sure this isn’t a legal thing, this is Google going “we got a takedown notice from this company and aren’t about to read it or hear your opinion, in order to protect ourselves legally”
