They evidently want some company, and certainly had the opportunity to establish some when they passed the gatekeeper, but they did not do so for a reason that did not they were willing to explain. I will say that sometimes instigating a conversation or friendship can take a certain amount of courage, so maybe the speaker is a coward? To refute this, I must once again refer to the third line of our poem "I passed the farthest light in the city" (3). This, along with his explorations of the "saddest" (4) places in the city, serves to demonstrate that our speaker is, in fact, courageous. Brave enough to venture where few people dare. It is therefore not for lack of courage that they turn their gaze away from that of the sentry, for they are blessed with more courage than others. They look down because they are not willing to explain something, and I would say that it is their night excursions that they are not willing to explain, because they are not able to explain that they like to be