So that they can understand ME! ha ha ha ha. 

I really don't think that English is the supreme of all languages. However, just like Spanish, English is very widespread. For instance, say you wish to travel to another country, and the likely hood of them knowing English is higher in Asian countries like Vietnam, S.Korea. In places like Netherlands, they also speak English there fluently, but I'm not so sure about Spanish. 

When you buy games or electronics, the languages are more commonly in English or Japanese.

These are a few reasons, but if you're not convinced, don't feel bad. There's many languages you can choose to learn based off of what your plans are in life. 

Try to learn Chinese, you know why everybody use English.

actually it s not very necessary... it all depends

If you travel a lot or you need to communicate with your business partners or... you like surfing Internet and need some info from original resources then you need English. 

and... probably if you want to be morden.

But nowadays it s not enough to speak English. Morden society requires at least 2 foreign languages...

Well, actually, to turn it into really proper haughty toidy English one would say, "Why does everyone need to speak English?" But that aint the way folks talks aboutit though. :) hee hee  (Please, that last little bit was a joke so don't go using aint and putting together words! I was having a little fun. In my English writing and grammar classes I was always taught that the proper usage was "to speak").

English is also not the most spoken language in the word. That would be Mandarin as it is spoken by more people than any other langauge. 

None of that matters though. The thing is that English (for now at least) will get you around in a lot of places you might want to go and get you around with a lot of things you might want to do. 

A while back the language was Latin for that. Before that it was Sanskrit. Eventually, it will be another language. 

For now, I'm very happy that it's English and I already know it, because it has to be a really tough language to learn with all that crazy spelling!