Could you imagine aliens rolling up in space ships near our level? They land in a rocket and then have to ask for fuel to leave. They have bulky pressure suits and have to shit their pants. They left their polluted and dying planet generations ago trying to settle a habitable world. They have been terrified for generations because they started detecting radio transmissions from their target planet. Later on they got a coherent enough signal to decrypt it and saw what they were going to end up dealing with was hostiles on another dying planet.