https://www.medicalnewstoday.com/articles/outdoor-play-children#why-it-matters

Sexism: A 2019 review notes that previous research has found that girls play outside less than boys. Some studies have found that caregivers treat girls differently from boys when it comes to managing risk, encouraging boys to deal with problems by themselves more often. This may mean girls feel less confident playing outside without supervision. Caregivers can also restrict girls from playing outside due to fears of assault.

https://news.exeter.ac.uk/faculty-of-health-and-life-sciences/by-aged-two-girls-are-already-playing-outside-less-than-boys/

The first national survey of play in preschool-aged children in Britain has found that from the age of two-years-old, girls are playing outside in nature less than boys.

https://slate.com/human-interest/2013/03/why-women-clean-more-than-men-because-they-re-judged-for-the-mess.html

Children need to play in the mud and get messy. It's good for them. But girls are being discouraged from playing outside. And being able, psychologically, to deal with mess is an important life skill needed for lots of jobs. Including being a doctor. It's better to learn these skills earlier rather than later.