Also important is... lots of times, when the adults or parents are going out to eat... it just so happens to be when a baby/child is naturally tired, or when it should be their nap time or bedtime. Thus, it's not actually great timing for them to eat nicely and sit still and for longer than 20 minutes in a restaurant.
And yes, when a baby/child is tired, AND in a restaurant AND there is a lot of external stimulation AND noise going on at the SAME time... well, they go bonkers. I wouldn't blame them.
They cannot be sitting all passive at this time.
For lots of parents, they "time" their going out or restaurant meals for more conducive times per their baby/child. Sure, you want a kid that is "portable" and "nice" at restaurants... but, each child has their limits as to what and how long THEY can handle sitting.
My kids are 2 & 6 yrs old. We still don't go to restaurants at certain times, or at all... because we know how our 2 year old is and what his patience is capable or not capable of...and we never go to a restaurant when either of our children are tired, because restaurants + tired children are like oil and water. My daughter also, simply CANNOT eat when she is fatigued or tired.... she has always been this way since a baby. Even if she is hungry, she cannot eat when she is tired/sleepy.
But this is common. All normal.
Good luck,
Susan