I know that Sea of Thieves doesn't want to do this main story trope, with one big story or goal. They want us to make our own story. But... who's to say our story doesn't wrap around other npcs?
NPC Story quests make many games interesting, usually with unique rewards for completing them, and multiple ways it can go. And since there are going to be towns within Sea of Thieves, and hopefully a lot more NPCs within them, and already being able to get voyages from the guild leaders, they already have the materials to do this.
I also bring this up because it can add depth to the game, adds lore even. Adds story and purpose for each and every island and character. And gives people the option to follow their stories. Not to mention shuts people up about the "I won't play this game because there is no story."
I fully believe Rare can make very interesting story arks with NPC quests, and give lots of lore about the sea of thieves.
