I think it’s just a hard social interaction, where a person knows that this is generally helpful to the problem, they want to help, but they can’t really be helpful unless they know the person incredibly well. They don’t want to say nothing, and what they should actually do (agree that the situation sucks, ask the person how they can help, be nonjudgmental when listening, and be willing to sit with them, help them with chores, or call them on a random Tuesday for coffee), feels like both too much and too little.
It’s the same problem when someone is going through a breakup or otherwise grieving, but for some reason, depression, chronic illness, and large weight loss, which are less commonly experienced and more personalized, attract a lot of this type of advice. A friend of mine at one point gained about 30 kilos while on chemotherapy for bone cancer, which is nuts, and she was working with several doctors on that, along with every other aspect of her life. Still, she was constantly given unprompted advice about how to incorporate lean meats and leafy greens into her diet. It might be generally good weight loss advice, but she only had 30% of her jawbone left.