I always look at the term 'natural' being used because people are uncomfortable using the word 'vaginal'. I don't think it's a comment at all on c-secs, or births involving drugs/intervention/surgery being 'unnatural', I think it's just that a lot of people are a bit squeamish about directly referring to genitals and reproductive organs and therefore use the term 'natural' to refer to a vaginal birth because it's 'impolite' to say 'vagina' lol.
I know I'm quite happy to say 'vaginal delivery' because hey, it's just a body part, but if a stranger or acquaintance were to ask me whether my kids were delivered vaginally I would probably be a bit for a second, it's so unusual to hear anybody other than doctors use the word, kwim?