I don't mind taking care of my mother, no father though, and regardless of her leaving me anything, I'll still do what I can. She is lucky and will have a pension $~1500/month plus social security in 5 years when she retires. I plan to retire in my 40s (about 15 years from now) but along with my estimated retirement needs, I'm also setting aside money for her too, I give her $500/month now and I don't really think anything of it. I don't feel bitter about it or regret it either. She doesn't have savings because she raised me and my sister as a single mother and while she will have a pension so she'll be covered financially, I still plan on giving her $500 (or more if I can afford it) because she'll leave it for us when she dies. If she needs it for long term care, then I won't mind her spending it all either. I'm not planning on needing an inheritance to retire since I was never planning on one anyways.
I don't see why children would feel slighted for making sure their parents are happy. Would you spend money to keep your children happy, or give them rags and scrap to eat while you put money away for yourself? I don't see it any differently, parents or wife/children they are all family to me. Sure I don't have kids right now but when/if I get them, I'll adjust plan accordingly.
I'm not sure how I feel about the saying "wouldn't subsidize behavior". Just because the parent doesn't want to work? Does that mean you are no longer able to help them out still? Sure if they are alcoholic/drugs then I'd provide living essentials like food. But a lifestyle choice of not saving money? It isn't my life and I have no need to try to control it. If money can't be given because parent can't spend it "according to your wishes", then let them know that you can provide them a roof/food if they need it but while living with you, they will help around the house/etc.
edit: I realise that I'm not as tight on money as other people are either. I'm only "paycheck to paycheck" because I save the rest of it. But my mother knows that and she doesn't expect me to give her money either. She saves what I give her and puts it into her savings and doesn't spend it. Though she's had to for my sister but even that I don't care about since it's no longer my money and it was to help pay her tuition.
edit again: Saw the comment about helping save for kid's college. This is more personal and all, but why should she? College kids are adults, young/immature (at 18) but still adults. Parents shouldn't have to save for their kid's college. It's nice yes, but something that they should? No more than the children saving for their parent's retirement... which is about the same price. Fund a child's college or fund own retirement? Parent's may choose college for the child but the child may not recognize that by doing so, the parents maybe giving up their own retirement. Because college tuition is the same as a retirement fund if invested by the parents over XXX years to retirement... and then the children feels like they don't have to take care of their parents because they don't have enough to retire on? Sure they would, if they didn't have the child those decades ago. This is why I give my mother money and will continue doing so. She funded my life at the expense of her's, I see no reason not to return the act now that I'm making money.