when dwarf fortress had money for a very brief period (this was before I started playing it and back when you couldn't dig down at all), players ran into a problem: a functioning society does not require 100% of its members to be productive.

so you would end up with dwarves for whom there was no work available, but because there was no work available, they could not afford any of the abundant high quality food and clothing and other goods.

and from this starting scenario and essentially physics-mandated capitalism comes a logical solution found by players.

if dwarves must complete jobs in order to earn money that they can use to purchase comfort, but comfort is extremely abundant, the solution is to create jobs that don't produce anything

and because of how Dwarf Fortress works, "pull the lever" is a job.

so players found they could build a room full of levers, not attached to anything, and assign the task of pulling each lever on repeat to whoever was available.

dwarves who could not find work otherwise would walk into the room and flip their lever from side to side, accomplishing literally nothing, until they got bored or hungry or tired and left to use the money they had "earned" to rectify that.

Tarn Adams found it was a better solution to simply delete capitalism.

and that's the story of why Dwarf Fortress no longer has an economy.