Why to educate? Lots of songs have technical terms of some industry or trade? GUEST,jag

We are talking here about the 18th century Royal Navy. I can think of a certain section of the crew of any naval vessel in commission at the time who would be in urgent need of education - i.e. those press ganged into service who might never have been on a ship before in their lives. Their training was done on the job as there were no training establishments at the time.

The landmarks were well known reference locations that fitted into the song and were in use well before the song. EBarnacle

The landmarks would not have been known to people the length and breadth of Britain. The sequence given in the song teaches the order in which significant landmarks appear to any ship making it's way up channel.

Two lines in the chorus date the song to sometime in the 18th Century:

(a) We will rant and we'll roar like true British sailors,

(b) From Ushant to Scilly is thirty-five Leagues

The Ushant to Scilly information only became a matter of significance to the Royal Navy after the introduction of a certain strategy in the 18th Century.