I agree - it's really not-out-of-this-world to teach kids how to behave in restaurants. Of course a lot of it is based on what happens at home. If the kids generally eat pizza or chicken-nuggets in front of the TV, naturally it's unrealistic to expect them to automatically know how to behave in a sit-down restaurant.
I do remember when my kids were about 7 and 8, and we were visiting the tearoom at the Cranbrook Railway Museum (it's excellent if anyone is ever in the area of south-eastern BC). We'd all wanted a snack, and the boys asked if they were allowed to sit at a table by themselves, across from us. We said okay, and actually there were quite a few compliments given our way, usually by senior-people. It wasn't unprescedented-though, a few months earlier I'd gotten a similar compliment in church. I hadn't known that there was no SundaySchool that day, so they'd had to stay with me in the sanctuary. A very nice elderly gentleman complimented me on their behaviour. Well okay, they were most likely a bit bored, but did the fact that they weren't performing acrobaticcs among the pews deserve a compliment? I know I'm old-fashioned but I taught my kids that there are sometimes that you "sit down and shut up".