Well, just like those with handicap placards for hidden handicaps that may not be obvious to the eye--stroller travel systems are the same way.
My son was nearly 11 pounds at birth.
He outgrew his infant seat by the time he was 5 months old. But prior to that, if i am going to be at some place for a while--it was easier for me to transfer the car seat the foot or two to the stroller, but not lug the entire thing around.
I had at the time a very weak upper body and core muscles were non-existent so to say that carrying his infant seat was "back breaking work" isn't too far from the truth.
So if I opted to transport him, I would first consider if the restaurant would accomodate it and often they do--and that is the end of that. And then if he wakes up, he is in a safe place that he can hang while everyone eats and not occupying the whole table or teetering on a chair.
Of course after 5 months, I didn't have that luxury anymore and then we would transport him in his stroller for his safe place to sit during a meal.
Now--if I am just going into some place for a minute or two, that might be different. But when he was an infant, I stayed at my dds' dance class and the whole system would go in with me. It hasn't been an issue at our dance studio.
The Ruby Tuesdays mentioned above had idiotic servers IMHO. And we wonder why Disney counts infants in a Priority Seating Request.