Lack of Ship's Name

We have recently installed an AIS system on our PSV operating in Bass Strait Australia. The first thing I noticed was that about 1/3 to 1/2 of the ships detected were not using their name but putting their MMSI number in both name and MMSI positions. I wonder how many ships would reply to a call on chnl 16 to a MMSI number (how many OOW's would recognise their own number).