I like to make up weird theories in my head about it not being aliens but alternate earth people. What if every time it is actually a first-time visitor not knowing what it’s like here. They don’t expect us to have anything capable of bringing their experimental craft down and we do, to their surprise. Hence they always have different looking craft, different looking bodies, etc.
Please tell that to the git overlords at my work. They won’t approve a merge with even a single unnecessary capitalization.