Vegetarianism / veganism in women is an instinctive way of signalling that she's single because meat was provided by men. Broadcasting that she doesn't eat meat is a way of advertising that she's unowned and that some man should take possession of her. https://twitter.com/edoredoredore/status/1197167706321170438 …
Well obviously it doesn't apply in cultural contexts where it's traditional - it's not a signal in those cases.