Following a chat with my non medical friend - I'm a doctor and very aware that the general public don't really know what our job titles mean any more (FYs and STs). My past two jobs I have had to specifically ask to have Dr myname on my name badge as well as the generally meaningless st6 or 7.
Of course I introduce myself as 'my name, the children's doctor on the unit today' but my ID badge is so people know what I am as well as who I am. If I had not pushed for it I would be wearing a label saying 'myname st7' and nothing else which means sod all to anyone who matters (ie the people I care for and their families)