The issue with night bus working is straight forward from an operator point of view.

You need enough willing drivers to operate a rota, otherwise dotting night bus shifts around the rota will invariably result in drivers 'failing' and work being uncovered.

Most operators have an 'X' strikes within 'X' time period system before triggering attendance disciplinary, and these duties will be few and far between that failing every single one may not ever trigger.

Given drivers also generally don't like working lates for the most part (bar a very small number), the percentage of the workforce who would reliably work overnight is tiny, even with significant financial incentives, certainly nowhere near the number needed to operate a basic nighttime network. It's simply not the operating model current drivers in this part of the country are used to, so I cannot see any acceptance of it either.

Take that workforce risk into account, higher pay rates needed to make it attractive, 24-hour engineering and supervision required, the actual cost per bus is absolutely massive compared to daytime operation and will nowhere near be viable.

Simply for that basis, operators tend to see them as very high risk and the immediate reward simply isn't high enough to be worth it.