I don't personally condone eating nude in public in a restaurant, but there is a broad spectrum of ambivalence towards nudity. For instance, plenty of europe is fine with mixed sex nude saunas and beaches. And the whole thing is pretty asexual.
If you feel ashamed or self conscious or indecent topless on the beach, or even in a same sex changing room, it's probably not a stretch to think you may feel shame breastfeeding on the side of the road in a car.
Now you will have prudes and exhibitionists in any society but the window of normality is going to be a function of what the environment dictates. And iirc being topless on a beach in the US is illegal, whereas no one will blink in Spain or France at a topless woman (except the American/Brit on holiday)
But this is learned behaviour - most children don't care about being dressed or not
When thinking about it, personally, although I'm a man, I'd feel a bit socially anxious / worried about what others would think, if I was without a t-shirt in a restaurant.
> learned behaviour - most children don't care about being dressed or not
(Actually I cared "a lot" and was disappointed when I had to start wearing bath shorts)
Do you really need to ask though?
When there's a topless woman in the middle of a restaurant, 99% of people are going to feel something is off.
There's a not-so-subtle difference between 'breastfeeding' and 'I'm going to leave my boobs hanging out while I set my baby down and get something out of my bag'
If you were in a restaurant, and someone was dangling their breasts for everyone to see (even a man for that matter) it would seem really odd.
I've seen women breastfeeding in public (airplanes, cafes) countless times, and I don't think anyone ever batted an eye, but there was always a shade of discretion.
A woman dangling her breasts around in restaurant, on the other hand, is a different thing entirely.
It's kind of ridiculous that we have a social protocol wherein nudity would not be appropriate in a given context, but then because of some specific need, that this protocol goes away. No. Nobody minds at all that someone is breastfeeding but people do mind fairly obvious nudity.
And I really don't think there's a soul in California who cares that a woman is breastfeeding or pumping milk in their car.