In almost every case, it’s because the entity that owns it doesn’t actually have to use it daily, because then you know they’d fight to get whatever safety measures they can cram into it.
Last city I lived in had a new intersection put in with a 2 way stop (only one of the roads stops, and you have to yield to main road traffic)
After tons of minor accidents and altercations arising from disgruntled people having to swerve or slam on brakes, the city out out a statement saying basically they’ve done studies and it’s safer than other intersections so nothing will be done to it.
Two or three years go by and one of the city council people moved and now has to use that intersection.
Within a month it had stoplights installed without a word.
Could be a coincidence. Maybe they even had been planning that for the entire two or three years.
But I personally believe nobody gave a shit until an “important” person (you know, that high-stake, much coveted small town council seat) had to use the intersection.