Servers very much distrust the client. Obviously. That's literally rule #1. Don't trust the client!
Comments like yours are extremely irritating. Please don't behave this way with your co-workers.
Anyhow, there's all kinds of types of cheats for different kinds of games. There's a variety of mitigations for each kind. I don't think there's a multiplayer shooter on the planet that has fully solved aimbots. For however clever you think you are I promise the cheat makers are much, much more clever. :)