It's kind of like the members of the French nobility who vied to have the honor of taking King Louis' night soil out of his chambers. It meant that every day they would have ACCESS to the King himself right in the morning when he was fresh and before others could tell him gossip about themselves!
Sure, both of us would have been in there begging to be allowed to draw water for the Temple, particularly the Chief Priest!
If you have not read the story I suggest that you do. It is very good with some nice twists.
The Gibeonites were slave not the holders of any monopoly.
“Now therefore ye [are] cursed, and there shall none of you be freed from being bondmen, and hewers of wood and drawers of water for the house of my God.” (Jos. 9:23)
This was punishment for their deception.
And their water drawing and wood cutting was not just for the temple as vs. 27 says,
“And Joshua made them that day hewers of wood and drawers of water for the congregation, and for the altar of the LORD, even unto this day, in the place which he should choose.”
So it was either do the work or get the chop.