How often do women masturbate and how important do you think this is?

EDIT: I guess I should say this is more a question for women. Guys, I know you all jerk off 3 times a day, thanks.

EDIT2: we're mid-30's. I wonder if age is a factor.

My wife says she NEVER plays with herself. Like ever. She has no problems climaxing when we play manually, or sex, or toys, etc... but she says she never explores when she's alone.

I kind of think this is important for people to do and I think it would help her loosen up (no pun intended you dirty people!) a bit and be a bit more playful in the bedroom. Like if we had sex she wouldn't go down on me right after, she'll use a toy in front of me but never seen her use her hand...things like that.

What's the general thoughts on this?