Says I.
Daughters can take care of them but my parents feel more comfortable with me than they would with their son in law… thats how things are in many households. I do not want MY parents to be taken care by a third person.
For me taking care of the parents means having them in same home, eating with them on the same table, being there when they are ill and make sure all their needs are met… not many SILs would do that, because? It is possible that they have their own parents to take care of and their own family responsibilities and I wouldn’t want my parents to be sidelined in the process.