he smiles when he remembers being electrocuted simply because his father came back....luke really had a lot of trauma after the ot... https://twitter.com/skywalkermyth/status/1275877785597284353

like owen didn't treat him like a family member but more of a slave, he saw a father in biggs who was only 5 years older than him. when he finally meets vader and hears that he is his father, after losing his hand, he automatically accepts this

like i think the reason he covers his prosthetic hand is a part of himself is still angry at vader, his father, for taking that part of himself away from him. his heart seeks his father, blindly, while logic tries to show him what he has lost because of him.