How we change what others think, feel, believe and do
People in crowded cities are constantly bombarded with stimuli and demands on their attention. They thus tend to keep themselves to themselves more than country folk. You can easily be quite alone in the middle of a multi-million-person city.
Cities also have higher crime rates, which are well publicized. People are squashed together in trains and shops and their body-space, outside of which they prefer to keep other people, is smaller than country folk.
You might think that this makes city folk less altruistic, but studies have shown that this is not true.
Consider the number of places in cities where single and lonely people can meet. There are singles bars, clubs, societies etc. Just look at the lonely hearts columns in newspapers.
In urban environments, give people the chance to show that they are individuals and not just statistics. Utilize apparent threats and then ask for help.
If you are feeling alone in the city, beware of the sharks who will prey on your fears. Seek out real friends and ask their opinions when feeling coerced by others.