More info is here:
https://www.nolo.com/legal-encyclopedia/your-obligation-pay-...
Because Wikipedia only talks about their existence, not a discussion of them.
I have to imagine that it's pretty rare, and I don't think it's appropriate to generalize from what appears to be a pretty sensationalist case. I expect the laws are usually structured to ensure that children don't fleece their parents out of money and turn them effectively into wards of the state, etc. It doesn't seem unreasonable to me that states would encourage families to take care of each other, though PA seems a bit of an outlier in this regard.
Typically when it's used it's to recover money in cases of fraud. For example, where the parent or child conspires to hide money from the state to avoid paying for care. To the best of my knowledge, PA is one of the only states that allows private entities to sue. Some states are like Ohio where it's a criminal statute, so only the state has standing to bring charges. All said, don't get legal advice on the internet, this is an armchair discussion by laypeople.
As an aside, I don't see why the children should have any specific burden to take care of their parents medical expenses now that we have Medicare and Social Security. We've decided it's better to have all of society to take care of our elderly rather than tie it to their children's ability to pay.