The people are also -- in general -- much friendlier.

This is the biggest factor for me as someone who grew up in Texas and is now in Los Angeles

I feel like this happens in cities with a lot of transplants. Most people move to big cities because they are (or think they are) the best at what they do. That makes it difficult for me to know who to trust since I don't know off the bat if someone is talking to me because they are genuinely nice or because they want to see if I can be used to help them achieve their goals. It's a vicious cycle because it causes me to put my guard up and in turn be less friendly than I am with people I really know.