Being able to read body language is a powerful tool to have in your social toolbox. After all, meeting people can be pants-shittingly intimidating at times. You want them to like you. Sometimes you want them to like you like you. You don’t want to end up annoying them, creeping them out or otherwise fucking up meeting a potential new friend or partner. At the same time, you can’t read their minds to gauge how they’re feeling about you. Being able to read their body language, on the other hand, gives you the insight you crave.
Now, despite what movies and TV will tell you, reading body language isn’t like doing a Sherlock scan on someone. You’re not going to be astounding people with your telepathic party tricks. But if you want to have a better sense of how someone feels or what they think about you, being able to read their body language will help you out.