It's not a theory for long because someone is going to prove it really soon, but I truly believe that there is a hormonal shift in women around the time their biological clock starts ticking that also makes them afraid to fly, afraid of heights, and nauseated on swingsets and other things that used to be fun.
I have empirical evidence from at least 7 people that backs this up.
I suspect that Montana doesn't actually exist. They take pictures of Wyoming and call it Montana. I've never been to Montana, I've never met anyone who's been to Montana, and those who claim to have been to Montana are stooges planted by the Wyoming crowd to convince us all of the reality of Montana.