I don't think you're right that society doesn't have canned responses for this sort of situation. There's no canned response as brief as "my condolences" or "I'm sorry for your loss", but combine a few vague phrases of the sort "what an awful situation", "it must be horrible to lose control over your body and mind like that" and something about how brave and kind the other person is for helping his grandfather like that, and most people are going to get through the conversation without too much discomfort.
It might sound like I'm being ironic, but even if these phrases are cliched and almost contentless in a strict sense, they're very useful for signalling purposes, and when you're talking to someone whose relative is sick or dead, being able to smoothly signal that you care is actually really good for both parties -- comforting for the recipient and convenient for the sender (in the sense that they can easily make their concern and care for the recipient clear without too much hassle).
It might sound like I'm being ironic, but even if these phrases are cliched and almost contentless in a strict sense, they're very useful for signalling purposes, and when you're talking to someone whose relative is sick or dead, being able to smoothly signal that you care is actually really good for both parties -- comforting for the recipient and convenient for the sender (in the sense that they can easily make their concern and care for the recipient clear without too much hassle).