Since ~2010, the UK started cutting costs everywhere. Current costs were harder to cut, broadly speaking investments were cut more. Things like fixing roads was on the list - because a slightly broken road is still mostly usable. But of course that cascades quickly into an unmanageable mess of potholes. It's also one of those things where small frequent repairs are presumably cheaper in the long run than leaving things until you can't ignore them anymore, then having a major repair job to do.