For most small/recreational boaters, the term "Captain" only comes into
play when the crap hits the fan and you are describing the "person in
charge".
Many small/recreational boaters and Captains of small commercial vessels,
of long standing, are rightfully addressed as "Captain".
Most professional mariners of any size vessel, only require the title by
crew or those directly assoiated with their vessel's operation.....but this
is not hard and fast for all sizees of vessel.
I've never required that anyone call me "Captain", but Gawd help the stupid
SOB who called me by name if he/she was crew aboard a vessel that I was the
Master of, under my license.
Ashore, I never introduce myself as Captain SoandSo, unless I am in a
professional capacity or trying to intimidate/impress/cajol.
At any rate, many people call me "Captain" sometimes, others at all times,
and others, never......not all that important, as I generally take into
consideration the person, conditions, and state of my ego for the given
situation.

Just NEVER call me "Skipper"...that's a military term that has it's
justification within the military, but as far as I'm concerned, it's the
ultimate insult in the civilian world of professional mariners!!!