Except for grass and most trees, suburban foliage is often quite toxic. A lot of your ornamental plants are poisonous. Think lilies, foxglove, Solomon's seal, and all the excitement of morning glories. The basic understanding that you don't eat anything you can't identify as edible is important in the suburbs too.
I don't disagree, but I'd say there's not really a big problem with people or kids trying to eat flowers. Foxglove and solomon's seal are dangerous but they also don't grow where I'm at. Lilies and morning glory do grow here, and they are also not terribly dangerous to humans (without eating a lot of them.)
Where I'm at, particularly in the suburbs, there's a distinct lack of things that are tempting to eat (like a berry) and also poisonous.
I think it's understandable. I live in a city suburb and the foliage around me is pretty much all non-toxic.
I was raised in a rural community and went camping often so we had the lessons of "don't eat random shit, you'll die" drummed into us.