Everyone wants to be understood. It is hard coming to a foreign country, or visiting one, having little practical exposure to the language. Everyday things like going to the grocery store or going to school can be difficult because of language barriers, and wouldn't you be frustrated if you went to a grocer in another language and couldn't find the aisle for something because you didn't know what the signs said?
It is beneficial for newcomers to find some people who can help them by speaking the language they've grown up with. It is also good for the foreign language-learning English speaker, who builds skills and confidence with the language by being helpful and applying the language to practical things like that. Not to mention that it makes online game play, forums, and chatting much less frustrating when you can understand what your fellow players are saying in their own language.
It's easy to read books in English on another society and culture, but while they seem interesting, there is no way to get a full understanding of these things without some type of immersion. Knowing the language of a place gives you an "insider's view" of its culture and society, and the people, if you ever visit somewhere they don't speak English; not to