And if the federated server you are on goes down. You lose everything. If the federated server you are on steals your information or censors you there is nothing you can do.
You have to choose a server that you trust. In centralized systems, you have no choice at all. If you can't find a trusted server, you can set up your own, ask a friend to do it for you, or pay someone to do this job. You are not bound to an artificial monopoly.
And Big Tech are the one who host your account on thousands of servers versus federation where it lives on one. If that one server host gets sued or ddosed you will be unable to lose your account. Meanwhile Big Tech can withstand DDOS attacks and lawsuits.