Etherium is a better coin since it also has the smart contract feature. There is nothing that you can do with bitcoin but you cant with etherium. So why not all people sell their bitcoin and buy etherium.
First, everybody has their own mindset and strategy, we can push everybody to do something without their permission. Second, it's their money, you can't do anything about it. Third, maybe they has bad experience with buy etherium maybe loss or holding too long. Last one, ask to yourself if your analyze wrong and they were wright, should they follow you? Have a nice day.