Most doctors are called 'GPs', for 'General Practitioners' and the medical service they run is called a 'practice'. When we refer to a 'family practice' we mean one that is for ordinary people - families, in other words. The idea is that they are friends and general advisers for the people they treat as well as just doctors.
Isn't it slightly unnerving that doctors are always practicing? Does this mena they never actually get to be any good? Same goes for Lawyers as well doesn't it?