Different demographics have different interests, experiences, and knowledge. It's trivially obvious that getting a broader subset of society to contribute will also broaden the content.
With less than 10% of editors being women, for example, content is guaranteed to be somewhat skewed, even assuming absolutely no ill will by anybody.
Among the famous examples are a scientist's entry being deleted as "not notable" just weeks before she won the Nobel Prize. Or, if you prefer quantitative data, that articles about women tend to emphasise their relationships and children (https://arxiv.org/pdf/1501.06307v2.pdf).
Wikipedia wants to be an encyclopedia though, not a bag of personal anecdotes and life experiences.