My DH and MIL had a house on a road like this. Being unadopted basically meant no council upkeep whatsoever; no drainage/gutters, no street lighting, no pavements, no tarmac. The bin lorry did use it and empty bins outside people's properties fortunately, but it was still awkward at night in the pitch black (it was like through a woodland, basically).
It was used heavily for people walking and emptying their dogs, which often were off lead and just ran around in people's gardens, pooing where they liked and generally not cleaned up after, possibly because with no pavements, it wasn't "residential" enough for them to think they ought to.
The road itself was just solid sandstone but it got hollows worn out and the residents filled them with road planings, which just wore them deeper. There were loads of arguments about the best way of maintaining the road (some didn't want the potholes filled, some wanted it tarmacked, some didn't because they'd get youths doing car races down it, etc) and some residents weren't great at paying their subs promptly.
It was very, very messy compared to living on an adopted road, and I wouldn't want to be involved in it. And DH is very "never again"...