I have sat next to plenty of people who "smell bad or play loud music or act out in inappropriate ways" in London or NYC. The differentiating factor (for me at least) is that those cities provide a legitimate service level with public transit that can get me to almost any place in their city in a reasonable time frame. That allows more "regular" people to forgo cars completely in favor of public transit. In LA it is much more difficult to live without a car and rely totally on public transit. Therefore many have already invested in a car. This makes the choice between using that car over public transit for any individual trip much more slanted in favor of using your car.