Because he’s not their relative or friend - and if he could have them killed to sell their organs for a dollar, he’d do so without blinking.

Hairstyle is a big part of most people's identity, and a disease, or anyway it's treatment, strips it away. People shave because their hair falls out like their body is just giving up. With the hair goes the ability to keep your sickness private. Everyone you know, and most people you come into contact with will know you're going through something big, and they will treat you differently. You're not you anymore. You're sick. Friends or family might try to show you it's not such a big deal by shaving their own heads, but strangers won't do that.

Let's contrast that with trump. His body isn't failing anymore than it already was. This doesn't strip him of his identity. If anything it solidifies it. This doesn't change the way people interact with him. This doesn't divulge any information about him that wasn't already public, by his own choice. Given his obvious insecurities, we would know if his ears were one of them and they are not. These people have no personal relationship with him. This isn't about making him feel better. It's about these people's own identity and demonstrating group solidarity.