Another aspect of my game that mirrors the West Marches campaign is the idea of "No Town Game."
A couple of quotes sum it up:
"make town safe and the wilds wild — Having the town be physically secure (walled or in some cases protected by natural features like rivers or mountains) is very useful for making a sharp “town = safe / wilderness = danger” distinction. Draconian law enforcement inside town, coupled with zero enforcement in the wilds outside town, also helps. Once you are outside the town you are on your own."
"the adventure is in the wilderness, not the town — As per the discussion of NPCs above, be careful not to change the focus to urban adventure instead of exploration. "
Both of those describe the four "town" settings my PCs have dealt with: Falcon's Keep, Swampsedge, the pilgrim's camp (aka "Rumshackles"), and of course, Stericksburg.
To be fair, some of this is a basic feature of GURPS Dungeon Fantasy as-written: town is vague and resolved with die rolls and simple effects. Town is safe unless you choose to make a roll and blow it. Town is where adventurers gather and get a minimum of information of the world around them, enough to send them off on an adventure.
Mine is a big less minimal than that, since we've got a big rumors table and sages for hire and recurring town NPCs of mostly color-level importance. But it's otherwise the same: safe, abstract, and not a place where adventure happens.
Again, the reasoning is the same - if you make town a place of adventure, people will adventure there instead. There is always one more thing to do in town anyway, even when the PCs are leaving. Ask this one guy something. Buy one more potion. Check to see if one more spell stone is for sale. Double-check if everyone has enough rope. Check and see if there just happens to be one more hireling ready. Adding actual adventure will mean you spend more time in town and less in the dungeon. Adding important adventures means you'll turn the focus from the dungeon to the town.
And that's fine, for a town-centered game. Or a town-and-dungeon game. Or a game where dungeons provide clues and links and resources that influence town. But not for a game where the dungeon is the thing, and town is a way to allow people to replenish and recharge between delves.