Also, as Harry himself speculates, muggleborns, like his mother, probably tend to fall into the habit of not thinking of muggles as Real People anymore, because it’s too emotionally taxing, and they’re living in a different world. They may stop concerning themselves with the muggle world much by the time they’re grown up. The muggle raised wizards in the original canon certainly seemed to.
Also, as Harry himself speculates, muggleborns, like his mother, probably tend to fall into the habit of not thinking of muggles as Real People anymore, because it’s too emotionally taxing, and they’re living in a different world. They may stop concerning themselves with the muggle world much by the time they’re grown up. The muggle raised wizards in the original canon certainly seemed to.