It's not about "looking after your members" or "selling out". Passenger TOCS live in a completely different world from everyone else when it comes to industrial action. Can you really not see that?
In virtually any other industry, losing a days pay for the workers and a days revenue for the company is just a minor side effect of industrial action, the real damage is that if the disruption continues, all your customers will leave and they will never come back.
Meanwhile at a company like Northern, which has a government-protected monopoly and a captive market, the drivers effectively have guaranteed jobs for life barring a complete economic meltdown, and the company suffers only limited financial damage from industrial action. Consequently the unions have no reason not to hold out for anything they can get, and the company has no incentive to compromise.
If ASLEF were to try their tactics in any other industry, and the management refused to make any concessions, all their members would be out of a job within weeks.
I actually think the reaons for poor state of industrial relations on the railways lay on both sides of the table, since neither side has any incentive to compromise.
However, for those of us outside the railway bubble, where employees and employers for the most part need to work together to make the company a success(or lose their jobs!), where agreeing to reasonable requests from your employer is the norm, it's sad to see the amount of inefficency in the rail industry, the level of resistance to tackling it, and the attitude that any change is an opportunity to extract as many concessions as possible from the company. It doesn't help that many railway workers seem to be completely oblivious to the fact that the reason they are so successful in industrial relations is not a strong union, but that no matter how unhappy the passengers are, most have no realistic alternative but to use the train.