Absolutely. My parents would willingly do it. But not me, and why the hell would I want to traumatize my kids more by killing off their grandparents? My kids talk to my parents every now and then and they would be crushed if they knew that their grandparents' death was because they needed a social life.
When you start rationalizing the death of older and weaker people so that the younger has a better quality of life, that's not a world I want to live in.