I get all that I do. They still raised you and paid your way. Now you're doing ok for yourself and just fk'em?
I'm sorry, I don't know your history. Still feels pretty damn selfish.
The only thing I will add here is that Parents choose to be parents (Well mistakes can happen, but adults must live with those choices regardless). Children don't choose to have deadbeat parents.
As the parent, you have kids and give them everything that you care to give them, without any expectation of return. If the amount you give and the relationship that you foster with your children, does not instill in them a burning need to make sure that you are looked after in your old age, well mission failed.
The funny thing is, most strained parent child relationships come to a head as the child hits that "Leaving home" age. Each parent will choose a different path at this point. OP's parents chose kick out the house and go to the army. OP got his life straight, in one form or another. But the crucial step that it sounds like his parents did not do, is re-open the lines of communication once he became an "Adult".
Perhaps explaining their thinking and asking his adult self for forgiveness at having to ship him off to the army. Guaranteed OP would have appreciated and forgiven his parents for that. With the hindsight that we all gain once we have children of our own, we can appreciate our parents' struggle and sacrifice.
Any child that is figuratively, literally, or emotionally abandoned by their parent(s); even for a good reason or to a good end; simply wants to hear from their parent's that the decision was a difficult one and that it hurt them as much or far worse than it hurt the child. That communication needs to be initiated by the parent, and if they didn't do that, they made a massive mistake. One that has allowed an angry young man to grow older and find that, without adequate reconciliation from the parents to extinguish that anger, he had to cover it up with indifference.
Not saying he should or shouldn't jump at the chance to help his parents. Just saying that either way he chooses to go, is the right way IMHO.