This mentality ties into why outlanders are welcomed into Krofberg. The outlander belongs to Krofberg, the suburb outside of the city. It is a commentary of the modern treatment of the lower class, that they are continuously shoved aside and removed as being undesirable. Referencing the laundress once more, the work is sent out of the city to distant suburbs. Similarly, bounty hunting represents the modern capital-driven economy where factory production replaced the economies of the quartier. You can't have a conversation around the Hausmannization of Paris without bringing up the economic system destroyed along with it. The new spectacle of the city, the splendor of the new storefronts, the new trend of window shopping. Looking for the sake of looking. Along with the spectacle came new trade, new items, new distractions. Consider the draw of the Orient, the new Japanese prints flooding the market at the time. Outlanders who bring in artifacts are partaking in the system of the spectacle.
To put this into context of the gate, the gate defines the new city space and guards the boulevards of the new city. By locking it at night, it reminds you that despite the superficial openness of the city, it is still a highly guarded entity. At night, the lower class is simply not trusted.
Oh hey class ended, forget this.