> Why would they be confused about a middle-man being present?
In some cases its because GrubHub created a website for the restaurant and they don't make it clear that it's a GrubHub site and not a site operated by the restaurant. If you call the phone number on that site, a GrubHub employee answers as if they are the restaurant.
Because Grubhub makes it sound like they're a delivery service that the restaurants hired. On their front page right now, for example, they say "we tell you the restaurants that deliver to that locale" - that's not an accurate description if Grubhub is the one deciding whether to deliver.
Grubhub uses "pickup restaurants" in its ordering UI to refer to restaurants where the final customer has to go pick up the food, so I don't think many consumers would understand this to refer to restaurants where Grubhub drivers do the pickup.
Secondly, are the customers not ordering the food from Grubhub? Why would they be confused about a middle-man being present?