Oh please. You don't think that just maybe UFOs have top secret electromagnetic jamming technology that fucks up the pictures even as they're taken? It's not that complicated. The NSA has had this shit since the early 80s.
The reason they're doing it is because the aliens are just off to the sides.
Landscape mode would reveal them, but they're cleverly hidden in portrait mode!
UFO is an identification. There isn't "do you believe or not". If the object cannot be identified, then it is an unidentified flying object, whether it is of alien origin or not. No ifs or buts about it.