I've seen too many anti-social loners who keep fighting the rest of the PCs to not go with them on adventures. They may think it's edgy and cool, but it's really just wasting everyone's time.
Yeah, that runs afoul of the Baron's Third Rule- "It is your job to tell me why your character is adventuring, not mine."
(First Rule is "Don't Be a Dick", Second is "The monsters are more likely to eat you if you're not a team.")
The process I go through when starting a campaign usually runs something like:
Step 1: "Am I running my long standing D&D game with my mutant version of AD&D?" - "Yes"*
Step 2: "What do you want to play?" Answer is usually "A campaign of adventure and exploration."
Step 3: "Any particular themes? Noble third children? Scrappy survivors with three coppers, some string, and a broken dagger?" They choose whatever, sometimes I present options.
Step 4: "What do I need to know about your characters?"
Step 5: "Any place you want to start?"
Step 6: "And, here we go!"
I provide three specific hooks depending on where they are and what they have told me about their characters. The goal is that they learn enough about the sandbox that they start choosing what what interests them the most, as well as gain contacts and allies that they may prefer. Those that already know about the setting often eschew these hooks. I also try to have 2-4 "secrets" for them to discover, with undiscovered secrets rolling over to the next campaign. Significant plot lines are seeded, with a timer as appropriate.
This last campaign, the grand story was the siege and investiture of the City-State of Shodan, throwing down the undead horror of the Ivory Queen. This occupied the PCs from levels 5-10, and has been done. The ancestral ruling family has taken control thanking the PCs for their aid. The rest of the party dog-piled the fighter who was promised a countess investiture for taking the city and ready for the Shodan family to tragically fall into a well full of swords. Whether or not this happens in the future is yet to be determined.
The next arc, chosen by a different player, is throwing down the Red-Eyed Walker (aka Ithaqua). It seems to be generating a large glacial shelf that has rolled over some civilization in the past, and currently threatens the city-state of a second player. The party is now 9-11th level, functionally as capable as 14th+ level from a 5e lens, I think. They first heard of this when the party was 3-4th level, and have been slowly investigating it as they party figured out how to deal with the first arc villain and plan for the second arc.
The first arc villain was a bit of an accident when the PCs did something I didn't expect, there were consequences, and they decided to pursue him. The second arc was chosen once they were exposed to the world and saw the pieces that were in motion. One of the players asked, "what do I have to do to become a baroness?" They found out, and decided to go the Great Deed route, picked an amenable duke, and did the deed. A consequence of not choosing a different route is that a frontier town was completely erased by a known hazard. This wasn't the PCs "fault", but it was a consequence of the problem being ignored. The third arc was chosen similarly, the PCs had a number of things that they had heard about and chose one that appealed.
The campaign may be retired during the summer, with a new one in the fall.** We'll have a new exchange student, and the fighter character is itchy to player something different.
* I present other options, but that's what is chosen.
**Which will be me. It's always me. There is a non-zero chance the fighter's player, who is new to gaming, may want to run something. We'll see.