Added to that, all women are vulnerable at certain times, whether or not they see themselves as such most of the time.
Anyone is vulnerable when undressed, ill or confined, and there are circumstances where all three of those states coincide (eg in a hospital ward). It is in places like that where many women feel that men (or the male-bodied) are not welcome. That has nothing to do with cultural assumptions about female attractiveness being a temptation, which you seem to be suggesting, Glorianny - but about the reality that a sick woman in a nightdress or hospital gown who may be connected to equipment is vulnerable by any definition of the word.
Places such as changing rooms and public conveniences have always been risky - we were warned against 'dirty old men', flashers and rapists as children, and as I have said on here before, as a student a friend of mine was sexually assaulted in a Ladies' in a bar, and that was all when a man going into these places would stand out (which is how things didn't go worse for my friend). Now that they can say they are women and lurk much more easily, what once were 'safe spaces' have become less so, and this is why there should be firm boundaries about who is allowed access.