As said, this really depends per country.
In Germany, dr (the PhD version) becomes a formal part of your name.
In NL, dr is a protected title, abused by MDs that did not receive a PhD.
Prof is worse. In NL, it is a protected title you should only use when you are an active professor.
In Italy, any teacher/professor, even at kindergarten, can be called a prof or a doctor and use that on their ID.
MD is not used in mainland Europe.
So if we do not want mr and mrs as prefix, why allow dr? (mr is a university title in the Netherlands as well... how confusing!)