Japanese Music In English

I've got a question, it's something I've been thinking about for awhile. I need someone to help me find the answers. So I'm posting this on the otaku.com to see if anyone can.
The question is, why do Japanese musical artists sing in Japanese and yet have a few English words mixed in their lyrics? Is it just because those words have no Japanese translation? Is it a pop culture thing? Are they placing a few English words to be more attractive to non-Japanese speaking fans?
I enjoy many Japanese artists, of many genres and all of them do the same thing. Forgive me if this seems a little obtuse but it's just something that's been making me curious for awhile. All replies and/or comments will be both respected and apprieciated. Thanks.

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