I have often found in Hong Kong that the written version of words are used in spoken context (while speaking Cantonese).

Being aware of the fact that Cantonese and written Chinese are pronounced differently, I am curious as to why the above happens and in what situations it does.

For example, in some popular Cantonese songs, such as '喜歡你' by Beyond, he literally says 喜歡你 (hei2 fun1 nei5 - I like you). However, the proper way in Cantonese to say I like you is (ngo5 oi3 nei5).

So, why does Beyond, among many popular cantopop singers, borrow from traditional Chinese in certain contexts?