Haven't you seen the adverts? You are always chatting and laughing with friends and family when washing up and cooking, and island appliances facilitate that.
Don't put your sink on the island, or your kitchen will frequently have dirty pans as a centrepiece. You don't need anything on it - especially if you fancy going for a nicer finish or stone worktop on the island.
Why?
Stove I can maybe understand but sink doesn’t make sense to me