Gemmel, I agree with you 100%. Had I ever been treated like that, I wouldn't feel any obligation. And if by some miracle your mother got better and money wasn't needed, they would continue to shun you.
I've seen this scenario a lot in the last couple of years. I know of one drama like this right now. The parents have basically disowned their adult (now "out of the truth" children). Suddenly they are elderly and need help, and there is no one. When I heard this I said, have they had any relationship with their children over the years and was told no, they didn't speak. If that's the case, then why should the children help now? You really do reap what you sow.
But I see that the bOrg is at the beginnings of a HUGE problem. No one has any savings, time, or energy to care for themselves or elderly parents who have been in for decades. No infrastructure or support offered by the bOrg.
And - they are all like selfish children. Most of them give almost no care to their elderly ones, even if they are all still "in". It's as if they don't have the emotional maturity to care. Very dysfunctional. The bOrg has made everyone into children (mentally), and they can't cope with this stage of life, or caring for each other. It's really disturbing to watch (as a "inactive one" looking in from the outside).