You have strategies which work for your
income and investment plan. Other people invest based on their income. If people find a personal investment strategy like you found, they could have profit when they are selling Bitcoin or any altcoins.
First of all. Where i said that i get 20% every year? oO I want don`t equal i get.
Second. I don`t know where you get statistics, i don`t have information about 2% or 5%. For me normal profit 7-12% per year. For my country it is normal profit. It is without cryptocurrency, just fiat money.
Third. I can decide what cryptocurrency i would buy/sell myself. x2 in BTC for 3-4 years would be good profit for me. Altcoins that can give huge profit can scam easily. Big altcoins wouldn`t give x10-x20.