why do song lyrics use incorrect Kanji?

many songs lyrics purposely use wrong Kanji, is there any reason for that?

For example, in 嵐's One Love, they use 時間 for とき instead of 時.

.... ?
I mean, I'm not a Japanese native speaker or anything, but this idiosyncracy has always clearly conveyed to me that they want the written meaning of the kanji to be the 'actual meaning' but in order to have lyrics that are more natural or more comprehensible when not reading along or better suited to rhythm and rhyme, they prefer to sing the 'incorrect' synonym.

I would say it is a kind of 当て字.
https://ja.wikipedia.org/wiki/当て字
Besides what defined in Japanese Wikipedia, in many manga and lyrics, sometimes different pronunciation for words (mostly written in kanji but sometimes even not restricted in kanji) is applied, to give the words certain connotation or just give some different expression from how it is written/read normally.

In case of 時間 with reading とき, whie the meaning is 時間 とき sounds more poetic.
(Though personally I do not see so much difference between the impressions 時 and 時間 give...)