Why do countries have different monetary policies?

Question

More specifically, Australia, Singapore and Hong Kong, links to references would be appreciated.

Answer 1

Different goals, different world views and different ideologies.
In Australia, the goal is a stable economy with "full employment", a population that has a relatively good standard of living, a society that is egalitarian and relatively free.

Singapore may want a free society but are not interests in it being egalitarian.

Hong Kong is a centralist economy and policies are not necessarily aimed at stability as prices can be controlled centrally.