A benefit of not having a deed is that you save silver by not paying deed upkeep, or the initial cost.
Not having a deed can be dangerous, as although your buildings cannot be destroyed, fences can be. Mobs can spawn on undeeded tiles, so one way to protect yourself is to have a guard tower, which will spawn up to 5 guards, depending on the quality of the tower. If the guard tower is rare, you will have 6 guards. Without a deed, you will be unable to brand your animals, so they are at risk of being taken or killed. Buildings and items that are not on a deed will take regular damage, and bulk containers will lose 5% volume per month. Without a deed, if you die, you will need to re-spawn at a starter village and make your way back to your settlement.