I think so, too. But there’s a vast difference between having someone choosing to give up what they were given, because of a disparity in parental care, and saying it should be expected.
I agree with the other posters that one cannot make a blanket set of rules for this sort of situation.
My maternal grandmother spent her last years living about five miles from my parents, and maybe 150 from her son’s family. Simply because of the proximity, my mother (and to a lesser extent my father) ended up providing much of the assistance she needed in those years: shopping, being carted to doctor’s appointments, and advice, and simply talking. My grandmother also was fairly well-to-do, even then. And even after having paid for my grandfather’s care after he couldn’t care for himself due to Alzheimer’s.
But, AFAIK, there was never any attempt by anyone to change the distribution of the estate because of that dichotomy. Had my parents ended up in proximity to my grandmother, because of the need to care for her, that might have been different, but as it was, it was simply a series of unrelated coincidences that brought everything together. My father’s company bought out a Rochester business, and so they moved here. My grandparents, at that time, were still living about 60 miles away on the farm they’d owned since before WWII. When my grandfather got too infirm to be kept at the farm, he was moved into a facility here in Rochester rather than the closer city of Syracuse simply because that’s where my grandmother grew up, and she was going to be more comfortable here, than in any other city. I won’t say that all involved weren’t relieved by the proximity my parents had to my grandmother, but at no point was it a planned factor.
In general, my grandmother didn’t like having to depend on people for assistance, she knew she needed it, but it grated, a little. So she’d try to take people out to lunch, when they did take her places. And, while most of the time that was my mother doing it - my uncle did step up often enough that it wasn’t unusual for him to do the same thing.
It also helps that my father’s family offered at least one stunning example of the madness that can happen when people start focusing on estates (even relatively minor ones) and who will get what.
sigh I really ought to talk to my sister about this, soon. Dammit. My mother looks good for many more years. My father… less so. My parents are full heirs to each other’s estates, but better to talk about things ahead of time. No matter how much I’d rather forget the whole damned issue.