@mrundkvist
First, a disclaimer: I love worldbuilding as an expression of the #ttrpg hobby, and putting a lot of effort into this makes it easier for me to improvise setting details when the PCs go off-script.
For me, random tables are a useful starting point which allow me to break out of my own habits and assumptions, similar to how I assign NPC gender randomly these days.
As an example, let's say I want to add a village to the map. I use the random tables from p. 159 in "Worlds Without End" to get a basic idea of what the village is all about. I get:
Rationale for the Village’s Existence: (8) "A bandit camp that went legitimate"
Who runs it? (8) "A pragmatic warlord"
Significant Locals: (10) "Native hedge mage"
A Current Pressing Problem: (1) "Vital food stores have been lost or stolen"
Local Likely to Interact with Adventurers: (3) "Gentry who wants no local gossip about their need"
Interesting Things the Place Can Offer Heroes: (1) "An unusually large amount of saved coinage"
And within a mere minute or two, I already have a vision of the place and some local flavor which I can use to improvise things when the PCs are poking around the place. And I can build upon these concepts and make the village more fleshed out if the PCs stay there for an extended time. I find this _tremendously_ useful.