I don't think they are playing "peek-a-boo." In fact the incidents with our military are rather brazen. They have done everything but shoot us down. On the other hand, there is a UFO case in which a launched ballistic missile allegedly did get shot down. It is claimed that a UFO encircled the missile and fired some type of laser beam to destroy it. There may be other cases that impacted our test programs -- events that the military would obviously want to keep from the public.
Why monitor the military? That is rather simple on two counts:
- Suppose you were observing the behaviors of a lower species. Some within the species are going about feeding themselves and reproducing peacefully. Others for some reason are trying to kill each other. Which group gains your attention?
- Incidents appear to have increased after WW2, and there seems to be particular interest at nuclear facilities, missile sites, and nuclear-power ships. As an outside observer you are thus seeing a major technological step change in human evolution. You might be concerned of a new threat to peace in the galaxy.
Per our current physics we now rely on nuclear power when an application requires a concentrated source of power. It's just expensive. It would seem likely to me that a more advanced species merely found a way to make it cheap.
Per the "peek-a-boo" thought, to me these incidents parallel what we would be doing if visiting a less developed planet. We would study the planet's biology, and try not to interfere with what occurs naturally. Otherwise we would be ruining the study itself. I think at least some of the abduction cases are for real. It's also not a stretch to imagine that a biological program might be interested in a hybrid species.
You can be willing to say "I don't know," but that doesn't make it any less sensible to look at the possibilities and run with what is most likely. Is there really much difference between "alien" and believing that this is something from another "dimension" -- what we might even call spiritual? In both cases we are going beyond the realm of the current human population. To me it seems a much greater stretch to think that ALL of these cases are of human origin.
The "higher creature" makes sense unless you believe that not only can humans develop exotic technology -- energy, materials, navigation -- with extreme speed, but then that all of the cases that involve witnesses of non-humans are patently FALSE. To me that is a huge stretch, a statistical improbability.
It seems much more likely to me that some other species in the galaxy merely advanced faster than humans have advanced, and we have not advanced enough to understand them.