When given the choice I always choose to use a large public restroom over single use private restrooms. This is the case for both restrooms and locker rooms. Showers, sinks and toilets are resources best used in the presence of others despite the privacy interdictions most people harbor around them. The possible infringements on ones own privacy must be preferred over the ghastly, trench-like conditions found in singe use spaces.
I would have assumed these preferences are obvious and widely held, but after further consultation with university peers, it is not the case. So of course, I must prove it through high level deduction and then through example (the latter just for fun story time).
The problem with singe use bathrooms is that they lack the passive forms of surveillance found in public space: other people. In singe use bathrooms the incentive to behave even half decently, to compose yourself, to settle into a state of decorum, to abstain from degrading the space into a unrecognizable defiled zone. Despite our self believed decency, left to our own devices, free from the gazes of others, we act like savages. Ill-mannered and incontinent. It is our state of nature. As a result the private space suffers, the environment is shaped by one uncontrollable hand without thought to others. He who uses the private bathroom is an individual without society. He is exists pre-civilization. Uncivilized. There is no authority but your own ego left unsupervised by a weak or even nonexistent super-ego. The Id reigns supreme.
The public bathroom is different. It is larger. It has more units and so allows for simultaneous use. Multiple individuals now come together in one combined space. They do not directly interact with one another but they complete similar actions in similar sequences. There is a recognition of this similarity by the individuals in the bathroom. "You are doing the same thing I am". Now how this recognition transforms into the creation of an authority which then establishes the conduct of action is not perfectly clear, but I will attempt to sketch out my theory.
There is some strong superior being in the bathroom. He is just better than the rest and the others recognize this. For some reason the evolutionary adaptations which made him biologically superior (in our species that usually means visibly stronger or smarter) a coincided with a particular preference he has in how he conducts himself in a bathroom setting (whether he washes his hands, the order in which he applies the soap, whether cleans up after himself after defecating, etc..). The others immediately recognize this character and mimic him because they realize that if they were in his position, if they were the stronger man, they would punish those who did not conform, who did not mimic. For this reason they copy this man and a status quo is a established. A way of acting is created. A bathroom culture. Repeated exposure to this external authority who sets the culture, creates an internalized authority (the super-ego) which then polices your past habits, forcing you to act in accordance with the cultural norm even when the strong man is not present. Any deviation from the norm triggers either a fear of punishment (carried out by the external authority) or a sense of guilt (triggered by the internalized authority). That way everyone acts the same in the large public restroom. They do not deviate because they fear the loss of love and recognition by their fellow bathroom users.
The uncertainty I spoke of earlier comes from two places. The first is why do we feel the need to mimic? Why is it that my fear of being punished is relieved by mimicking the leading authority. It could very well be that mimicking further enrages the superior. The second is why the stronger authority then ends up preferring cleanliness and order over chaos and disorder. Why is the bathroom not a war zone. I brought up the synergies in evolutionary adaptation, but this is just straight guessing.
Anyways maybe hesitate before walking into the single use bathroom. You never know what you will find.