The Captain

The Captain of a ship, sometimes called the Master of the ship, has been one of the most socially mobile leadership position in European countries for centuries.  The job is not reserved for nobility, like army officer positions are, and doesn't require the burden of having family as an alumnus as many guild leadership positions do.  Often a sailor that knows his stuff, and shows potential, can be elevated to a captain or some other "prestigious" position on an ocean going vessel.
Yet, the captain of a sailing-vessel needs to know everything about the ship.  They need to be socially aware of the crew as well as every crewman's job and how good they are at it.  They need to know the ship and how it's put together.  Every detail is ultimately their doing.  This includes any failures, since if a crewman fails at a task, the captain was the one that ultimately pays for it.  There are a lot of hidden concerns that a captain must take into consideration. Finally the captain is responsible for any legal issues with his ship or crew while it is in port.  He is the one brought to task if there are tax or shipping irregularities.
There are also some nice perks.  The captain gets a cabin and if there are more than one cabin aboard, his is closest to the deck and the largest by design. Sometimes, if the ship is big enough to have a large crew, some crew are assigned to attend his needs.  Often a young person (male or female) will be hired at a young age to be cabin boy under direct command and supervision of the captain, taking a cut in pay in trade for very valuable experience  The pay is quite good for a captain, and getting extra shares or bonuses for certain tasks is part of the arrangement.  Buccaneers, Pirates, and interestingly ships sailing out of Taino ports use a share system, of which the captain gets 2 equal shares for the burden of his responsibilities.

"I served under Commodore Holmes as a cabin boy, back when he was a captain himself.  He was good to me and I learned alot.  One day he sat me down and gave me the hard facts about being captain and what it meant.  He told me all about the responsibilities, but most of all he told me about the pride.  That responsibility isn't about proof, burden and guilt, but about being the source from which order, morale and success on the ship flows.  That's when I knew that was what I would be one day."
~ Captain Gwen Lovetree, HMS Defender, Ship of the Line