Indeed, and a road being closed doesn't prevent you from having that car or driving it on your own property, but paying for your car is not the same as paying for the road. Of those only VED and tax on fuel are even remotely related to paying for the road, but really that just goes into general taxation. Going by that same logic my 10 year old also pays directly for the road whenever he spends his pocket money on something with VAT on it
You're right it's a bit of a slippery slope, and while I agree that unforeseen circumstances such as extreme weather or a suicide are a bit of a grey area, but months worth of (seemingly) endless strikes and staff shortages can be planned for and avoided.
You mention drivers not turning up or calling in sick, but tbh I don't see that as a valid excuse for cancellations. A delay while a replacement is sorted maybe, but I learned the concept of "redundacy" for critical systems when I was still in college...