But the customers are ordering the food from Grubhub, no? So why would they be confused that there's a middle-man?
Grubhub literally says 'shows you restaurants that deliver to you', imply the restaurant is delivering, not Grubhub. Furthermore it implies if you order, you're ordering from the restaurant- where Grubhub may have put up that ordering entirely without their consent!
Why does Grubhub have any responsibility to obtain the restaurant's consent? If I pay someone to go to the grocers and pick up some items for me, is that someone obligated to obtain the grocers' permission? Why is this situation different?
If the restaurant is offering pickup service, then to me there is no obligation on any third party to obtain permission to utilize that service and deliver the results to a customer.