Trebuchets are/were not the only reason players use a ton of land claim around their bases. The biggest threat, up until recently, is what we always called “jump towers”.
You could basically wear epic heavy armor and jump from insane heights and live. Which allowed you to jump on top of people’s bases and then raid it top down, circumventing any of their defenses. The only way to stop it was to spam a ton of land claim around your base to prevent raiders from building jump towers right next to your base.