Repairing structures? (DS2)

I’m well over 100 hours in and trying to 5 star my remaining sites and I generally just built all the roads, monorails and mines as I went along and I’m yet to have repaired a single structure

It feels like the mechanic is very underbaked and unnecessary in an otherwise very polished game - I have like five sites left to finish and still the roads I built a hundred hours ago are holding firm. The structures deteriorate so slowly that the mechanic feels almost irrelevant.

Is there something I’m missing? Are the roads or monorails slower on lower durability or smth?