Many people in big cities don't know their neighbors because they're just too busy. With long work hours and commutes, there's hardly any time left for socializing. People are often juggling work, family, and other responsibilities, so meeting neighbors isn't a priority. Even on weekends, they might prefer to relax or run errands instead of trying to get to know the people living next door.

In big cities, the high population density makes it hard to know neighbors. There are so many people, and they often move in and out frequently. This constant change makes it difficult to form lasting relationships. People might feel overwhelmed by the number of residents and find it challenging to connect with others in such a transient environment.

Cultural differences can also be a reason why people in big cities don't know their neighbors. With diverse backgrounds and languages, there can be barriers to communication. People might feel hesitant to approach others due to different social norms and customs. There's also a fear of misunderstanding or offending someone, so they might prefer to socialize within their own cultural groups.

Technology and social media play a role in why people don't know their neighbors. Many spend more time online than interacting face-to-face. Social media offers a sense of community without needing physical interaction. People might prioritize online friendships over local connections, leading to a sense of isolation in real life. They may feel they already have enough social interaction through their online networks.