While you don't need to put a faction block on a entity. Docking an entity will inherit the faction of the entity your docking too or when you spawn it in you can set it to spawn in to your faction. So it seems like a block that isn't necessary. But there is actually a pretty good use for the block that some people might not know about.
The faction block has 99% armour and 255 HP meaning that this one block will take over 25,500 damage to kill not including damage going to Armour HP or defensive effects.
So this one block that you can only have once on each entity is the perfect block to protect the a single block that needs to survive. I typically use them to protect the docker from the front direction. So that my turrets are harder to disconnect from the ship.
The faction block has 99% armour and 255 HP meaning that this one block will take over 25,500 damage to kill not including damage going to Armour HP or defensive effects.
So this one block that you can only have once on each entity is the perfect block to protect the a single block that needs to survive. I typically use them to protect the docker from the front direction. So that my turrets are harder to disconnect from the ship.