Having been in and out of a lot of storage facilities - and not just when buying a unit or storing personally - I'd say that one of the reasons may be what each party stores.
A man is more likely to store valuables or things he at least values. He's also, I'd imagine, more likely to sell items he deems "worth" something in a time of need than a woman. I've known a lot of guys who store car parts, merchandise, their "mancave" items, etc. in a storage unit but very few who store their entire house or personal items. Most of the ones who I've known who DID store their whole house or personal items only did it because of financial ruin (divorce, loss of a house, what have you) or due to having far too much crap/a hoarding issue.
On the other hand, women it seems are more likely to store excess stuff, personal items they want but don't need, a relative's (kid, dead parent, whatever) junk to "go through later", etc. Plus, you have a lot of single mothers who may be forced to rent one due to financial or space constraints.
It being slightly skewed towards women doesn't surprise me, and I wouldn't be surprised if womens' units didn't go up for sale more often. That said, I don't think it is necessarially the fault of the women; finances or lack of interest in the stuff is more likely than pure flakiness.