more potty talk

I began pondering the port-a-potty a few months ago. I was at a Cowboy fast draw event that had two port-a-potties. One was pink, one the traditional blue. Upon closer examination each unit had the respective gendered restroom sign of cultural understanding. The pink woman's room also had a small mirror on the inside of the door, a feature apparently not included on the men's. Is it really necessary to have a separate men's and women's port-a-potty??
My port-a-potty-ponderings have returned in the last couple weeks as I've become a regular of such establishments. This is the restroom of the construction site (all blue w/ no gender specific signs). My curiosity is that the toilet seat has a spring. Not just the lid but the seat. It is in essence the reverse of the "don't leave the seat up" argument. There is no way to leave the seat down. Thus, there really is no squatting if one intends to use the seat b/c the rear must be used to keep the seat down. I have yet to decide the usefulness of this spring feature (on all the potties I've thus far used on sites). Each unit also has a 'urinal'. It does make me wonder why all those folks who keep ragging on others to put the seat down, don't just install the reverse. Install a spring that forces the seat back down. I don't know if one can pee standing up while holding the seat back as one is able to hold it down with the rear end...