My baby is only 9 months, but we're already all eating at the table together. I personally plan to always eat at the table, but let Friday night be a pizza in front of the TV kind of night, as a mini celebration to the end of the week, and relaxed way to start the weekend. I won't start this until maybe Y3 though.
I agree that children need to learn basic social etiquette and to eat without getting up and down. I think there can be slightly different rules for home and out. At home, I'd personally allow my child to go if they'd finished eating, asked politely, and put their dishes in the sink or etc. Restaurants you obviously have to sit still, but I'd be fine with a book or colouring when finished.
Letting children free roam in a restaurant isn't fair on other diners. If my 9mo is getting bored and angry, I personally pick her up and take her a brief walk (held walk) to the bathroom and show her around if toys aren't working, or to the bar. If it's nice I'd take her outside. When she's a toddler, if it was nice I'd also briefly take her outside for a little breather. Yes we all need to learn to sit at a table, but it's very unreasonable to expect children that young to remain at a table for a couple of hours. Just don't inconvenience other diners with it.
Holding very young children to the standards of adults is unfair. Most grown adults also like a break to stretch their legs in long boring situations, such as planes or work meetings. No normal person outside of this forum is going to be judging a woman walking her baby around a little if she isn't getting in the way. It's better than crying!