It's a consequence of globalisation. Don't just blame English though!
There are around 6900 languages spoken today around the world. However, thirty of them are spoken by over 60% of the world's population (4 billion people). The remaining 6870 languages are spoken by a combined total of only 2.5 billion. These languages tend to have only a small number speakers. As time passes, more and more of these languages will disappear.