Very often people in the US think they are the center of the world and every one should speak and write English and why bother having a multilingual website? The fact is that this is not true.
Studies show that:
Only 27% of internet users speak English
70% of internet traffic comes from non-English native countries
72% spend all or most of their time on websites in their own language
20 languages are required to reach 80% of the online population
72% are more likely to buy if they have information in their own language
56% said obtaining info in their own language is more important than price
English is not the world language yet and will most likely not become the dominant world language. When you are selling to the world, the benefits of localizing your website could be immeasurable.