I don't argue against the people who disagree with me, they are quite right. I don't have to commute to work and have a threat hanging over me if I don't turn up to work on time, for example. Actually, throughout my working life I never had to rely on commuting by train to work, so that probably means that I have an unrealistically rosy view of what travelling by train is!
But Northern (or any other rail company) can run 100% of its services with 2 members of staff if it wants to.
if it's allowed to get away with the "oops, sorry, but it's better to have a train with one member of staff than no train at all" approach then it means that for every 100 rostered staff it has to employ 105 staff (I'm making up numbers) because trains don't drive themselves yet.
If it's not allowed to get away with it then it has to employ 110 staff for every 100 rostered, which means that it's paying for more people to sit idle on "spare" turns when everyone booked turns up. That's a problem that it has to deal with. If it wants to be constructive it can come up with better ideas of what these "spare" staff can do instead of reading the paper in the mess room, or whatever. (For example, wouldn't it be nice if they could use their local knowledge as input to the timetable planning process?)
It's completely in the power of the train operating company,
Ultimately if employing 5% more people feeds through into increased fares but guarantees that all trains run and have two staff members on them, then it's a price I'm happy to pay. And some people won't be prepared to do so, that's fair enough.