Why not? Who could possibly predict alien motivations We can't even predict human behavior and about the only thing we can say is that obviously their motivations are somewhat obtuse when compared to human motivations. I think by now it should be apparent that they intend to be as cryptic as possible or maybe.. hell I can't even make up motivations that could accurately describe what we see other than to simply describe what we see.
Alien body parts? We cannot accurately say the "things" we see in the sky have bodies or parts, I happen to have my own prejudices in this. The wilder the sighting becomes the less creedence i give it. As soon as anthropomorphic aliens come into the picture my bullshit meter pegs off the scale. Anal probes on some deserted back roads or simply "beaming" into your bedroom at night and whisking you away for some genetic mixing of what should be a completely different biosphere. We should be far more closely matched to pine trees than aliens. If they can do these things right under our noses then they come very close to qualifying as gods and any efforts we make to figure this out should be shunted to the televangelists. I tend to stick with the more "mundane" if an alien spacecraft sighting can be called such.
Anything beyond physical craft that have to follow the same laws of physics as we do are virtually impossible to do anything about but speculate.
I would tend to stick to the hardest evidence, a simple unknown light in the sky is meaningless so is some redneck getting an anal probe while making out with bettylou on a side road...
I like to compare it to bigfoot, we have maybe one film/picture of bigfoot that is clear enough to really beggar the imagination. The Patterson film i think it's called, I remember the first time I saw it, my jaw hit the floor! WOW! Had to be real who in their right mind would travel that far into the wilderness carrying a costume and film it from horseback is such an amature way? Every frame of that film has been dissected by amateurs and professionals alike. Scientists have literally traveled the world to figure this out, motivated by one film made by two guys of somewhat questionable repute. That film is fake, a hoax, a man in a costume, the man who wore it has been identified and he admitted to it. The costume, so realistic at the time has been busted, even to the point of people coming forward to admit to making such a costume for the guys who made the film. The entire idea of bigfoot is based on on old legends, quick glimpses of something walking upright in the woods. Interestingly the most convincing sightings overlap black bear territory quite accurately.
Then you have the problem of a population large enough to propagate without genetic bottlenecking and if there is a population where are the road kills? In the US everything eventually ends up as road kill. Even animals unknown to science (subspecies really) have been found in road kill. Humans show up regularly in road kills, from bears to moose to humans road kill can be used to chart what animals live where. The "evidence" for bigfoot is much thinner, several orders of magnitude thinner than evidence for nuts and bolts UFOs. Yet both amateurs and professionals continue to beat this dead horse seemingly desperate for every scrap of anything. While there is some derision on taking bigfoot seriously many professionals continue to study this in their spare time based on almost nothing! I know shit from shinola, bigfoot is not shinola...
The main problem with UFOs, IMHO, is the paranormal aspects of it, from the contactees of the 50s, to the anal probes of, the 60s and on, to the world wide hoaxing of UFO sightings on youtube today, a huge amount of bullshit surrounds and covers any possible truth. The signal to noise ratio is ridiculous but it doesn't completely cover up the signal.
Most of the UFO phenomena is bullshit, I grew up on a farm in the mountains of WV, I know bullshit when I see it, in fact I know horse shit, cow shit, chicken shit, dog shit, deer shit, racoon shit, muskrat shit, mink shit... I know my shit, and under the layers of shit in the UFO phenomena lies something else. I'm not sure what but I want to dig it out, clean it up and run it up the flag pole and see who salutes it... Far too many people try to polish a turd when it comes to UFO sightings, i am not afriad to point out that a polished turd is still a turd and most of the current body of UFO sightings are definitely not shinola. But there remains a small body of data that will not go away, cannot be explained despite an embarrassment of data and evidently drives the US Air Force to lie and decieve not to mention suppress any real scientific study of the phenomena by ridicule and spreading the idea of incredulity... Literally the first real study of UFOs was dismissed due to the incredulity of the commanding officer who had no idea what a real scientific study was or should be...
Being dismissed out of hand is getting old, tackle the data honestly, it's the least we can do...