That and living in water. It seems much, much more difficult to develop tools and technology in an aquatic environment than in air. Just think about how poorl

That and living in water. It seems much, much more difficult to develop tools and technology in an aquatic environment than in air. Just think about how poorly almost any manufactured item performs, long-term, in water (corrosion, etc.). Of course, it's possible some aliens might develop underwater, like octopi, and develop technology. But I think it's far less likely than aliens that evolve on dry land.