According to this, roughly 1/5th to 1/3rd of heroin users get addicted: https://jamanetwork.com/journals/jamapsychiatry/fullarticle/...

A lot of the information is from back in the time where opium was legal but most people are not very receptive to opioids. They feel sick and tripping balls and would not repeat the experience if offered.

It is a very particular kind of person who gets addicted right away.

Of course, in a social context where consumption is expected, many more may reach the point where they keep consuming in order to stave off withdrawal.