@GMTplus7
Currently, everyone switches to English because it is the global business language. Because China is most likely to become the most powerful economy in the future, over time, Chinese will become the accepted business language. Even presently, if you know English, learning Chinese is more valuable than learning any other language. Generally, IMO from Chinese culture, Chinese people appreciate your effort to speak Chinese, even if you do not speak it well (as opposed to France, from my experience only).
@bomerr
I’m not sure why you think Chinese is a relatively less useful language. China has the second largest economy and is likely to become the largest. Even if OP forgets it through non-use over time, it would be easier for him to pick up should s/he want to.
EDIT: Also, while I would personally agree English is an easier language to learn than Chinese or Japanese, I do know that many Chinese people struggle with English. Just because English seems logical and easy to learn to you does not mean it is the same for everyone else.