I have worked at TGI Friday's, Cracker Barrel, O'Charlie's, Hooters, Ruby Tuesdays, and Longhorn Steakhouse. They ALL worked the way I described. The hostess took the order then handed it to a server to ring in, and then package for the customer. There were many, many nights I went home with less than 7% of my total sales because of a large number of take out orders jacking up the amount I had to tip out to the auxiliary staff, even though most take out customers believe that we don't deserve a tip for the time and effort required to put together a take out order. It is, by the way, a non-trivial amount of work.
The problem is that for me, as a customer, I have no way of knowing this. Absolutely none.
My assumption would have been that there were one or two people, maybe kitchen staff, designated to deal with the carry-out meals and that they were not waiting tables that night, but getting at least minimum wage and just working in back dealing with the carry-out meals. That wait staff were fitting this work in while waiting on tables would simply never cross my mind.
Really, I put the blame for this on the restaurants. They want to offer the carry-out service, but not pay any extra for it. And they aren't going to tell the customer that they still need to tip, because, as many people here have noted, the customers aren't seeing much service being performed (no matter how much actual work is involved, the customer does not see it) and therefore see no real need to tip, or tip significantly less than at a sit-down meal.
It's up to the restaurants, who created the problem, to solve it.