You have to consider the type of crimes. For a city of 7+ million, Hong Kong is very safe if you consider the relatively low number of serious and violent crimes (i.e murder, rape, armed robbery). But in terms of more "minor" property-related crimes like pickpocketing and shoplifting, it can be high in specific locales (i.e Causeway Bay, Mongkok). There are also quit a few fraud-related crimes, but they usually target the elderly and guillble. So you are right to feel safe walking on the streets in terms of personal safety. But, in terms of safeguarding property, better be more careful.