When I walked though a Dwemer Ruin I started to wonder why the creatures they build for working are so aggresive, is it because their makers dissapeared and no one sort of controls them now, do they just attack anyone that isn't a dwarf or some other reason?

Same reason there are traps in the middle of meeting halls.

They were paranoid little bastards.

Pretty sure they made it so that anything that isn't a Dwenmer gets attacked, though I don't exactly know how.