eh... They did put that slit in the underwear of men. However, I have seen women (not many) wearing mens underwear (never bothered to ask why - besides, my focus was higher up at that time).
Now, from personal experience, I have used the "dick slit" a few times. Not for any special reason other than to use it. Of course, it is mine and I could take my time in doing so. But, more often than not, I generally pull the elastic down and proceed to do my business from there (you don't want to fish around too long in a public restroom - it could draw some unwanted attention).
By the way... nice topic!
