I think most of the people replying on here agreed that there are lots of cases where they would just say yes, but there are also some cases where they would say the rule doesn't make sense. (Of course, being here, as a group we also then immediately start sounding like we are on a yes or no side without any of the qualifications or nuance).
As to why some folks might say no sometimes, here are some examples that I think should work for Sailor Background by RAW if the DM never throws in complications.
- When Chewie and Han are cornered and Boba Fett has them outgunned, all Chewie has to do is to start bargaining for passage on Fett's ship to Kashyyk for he and Han (because of course the Falcon is down for repairs).
- If Prince Humperdinck wants to capture the Dread Pirate Roberts, all he has to do is grab one of his sailors, row out to the Revenge, and when Wesley/Roberts gets ready to have him walk the plank the sailor bargains for passage for he and the prince back to Florin (where the entire fleet is just a bit off and ready to surround them).
- After Barbossa has Jack and Elizabeth walk the plank, Jack just needs to turn around in the water, invoke "Sailor Background" instead of "Parlay", and he and Swann can be ferried around to where-ever they were originally trying to get. ("Sailor Background is more of a rule than a guideline.")
- Percy and friends need Charon to ferry them across, but they lost their obols. No need to panic, turns out Grover actually has Sailor background! All they need to do is polish the floorboards on the trip across.
- The Brandywine barge man has heard all his life about the elven ships to the west. How could he ever get on one. And then he realizes, he can just bargain for passage!
Would those all get an unequivocal yes from you with no monkey's paws or loophole looking?
There are also some spells that many DMs would also say don't make sense in some cases by RAW and they would edit the rules in those cases to be either be more permissive or more restrictive. (But they wouldn't do anything to change them the vast majority of the time). I wonder if it happens less with spells because "it's magic" is a nice band-aid to make things just work. I wonder if "ghost ship crewmember" or "fairy kings burglar" or "aura of heroism" backgrounds would generally be allowed to work in more cases than "sailor" and "criminal" and "hero of the people" backgrounds.