Before learning a foreign language, we should first find out why people speak (even in their native language).  Do they really need to do so?
 
Well, it turns out that people speak to achieve a desirable result.  Perhaps the exception is that sometimes we speak to ourselves, but if you think about it, even that can yield a result.  When learning a foreign language, for instance, we tend to talk to ourselves, and this peculiar behaviour allows us to learn what we need to learn.
 
Now, I do not want to step back from the previous claim, but the truth is that people can do very well without conversing with others.  If the situation is one in which everything is happening on its own, and you do not need anything other than what you have received already, then you do not need to speak.
 
When people are with others, though, they create situations which force them to talk.  They pose questions to receive something that they need or the information which they require.  People answer questions so as to feel proud about helping someone else.  People recite long poems to create amazement, they tell jokes to get others to laugh, they speak to a schoolchild, student or an interesting audience for educational purposes, sometimes they simply babble to keep up a conversation and to satisfy the communicative needs which are of such vital importance to people, etc.  This means that people who talk always have a goal – achieving a material, informative or, most importantly, desirable result.