Because women don't get to have "man caves"
Once in awhile, even I'm surprised by the pushback I get, especially when I think an idea I have is kind of obvious. A lot of people wanted to quibble with my idea that women read more than men because women are under a lot more pressure to have hobbies that are unobtrusive and interruptable. Part of the pushback was classic "not my Nigel!", of course. Some of it was women who extrapolate from their own personal experience too much, and assume incorrectly that most women have as much control over their lives and free time as they, the lucky rare ones, do. And most of it was basically just "Nuh-uh!" or "sometimes men don't get to play video games for 10 hours straight without anyone walking in front of the TV and vaguely annoying them", which is sort of beside the point, since my point was that women often just find it easier and more enjoyable to have hobbies that can literally be dropped at a moment's notice. Behavioral psychology does apply here; if women find that TV watching and video game playing have too high a price to be paid in terms of family members whining or arguments with spouses, women will start to move towards hobbies like reading that don't piss anyone off.