That reads like pick-pocket advise for any country, it might fit New York City or Paris subways as well.

https://en.wikivoyage.org/wiki/New_York_City#Stay_safe "The most common crime against tourists (not including being overcharged!) is bag snatching. Never let go of your handbag (putting other bags down is OK, as long as you guard them carefully), especially in the subway but also when eating at a restaurant. Take special care if sitting outdoors or in a crowded self-service restaurant. Leave your passport and other valuables that you don't need to carry in a hotel safe or hidden in your suitcase. Don't flaunt a wad of money if you can help it; if you want to be safer, count your money in your room before you go out and take only what you think you may need. Unless you have protective outer wear, consider not wearing expensive jewelry, and hide valuables like cameras when you're not using them. [...] While muggings are rare, they do happen."

https://en.wikivoyage.org/wiki/Paris#Stay_safe "The métro is also a popular place for pickpockets. Hold things tightly and be aware of your surroundings. [...] Pickpockets are most likely to be found working at crowded tourists hotspots, so keep your wallet and phone in your front pockets and hold your backpack tightly when in a crowd."