why do they say it that way?

[M_aria]

How come certain artists who's English is good or are very fluent choose to pronounce English words in songs with an accent? Does it have to do with the music arrangement? or is it meant for people who aren't fluent in English so they can sing along? Anyone have any ideas? The reason I'm asking is because I was listening to Hikki's Heart Station and I wondered why she says "Heart Station" that way but the English in Flavor of Life and Beautiful World is without an accent