Your using Singapore as an example is poor.
Most younger singaporeans use English as their first language. Many have very poor Chinese standard. They might be able to speak the language (either in Hokkien or Mandarin) but they are not really good at writing. So I do not think most singaporeans are "bilingual".
On the other hand, Chinese language is first language to local Hong Kong Chinese. And thus it make sense for people to use mainly cantonese, and learn chinese using cantonese.
In any case, go take over this discussion if you want. Have a good day.