system
Given the following post, respond as if you're commenting on Reddit:
human
In shows were odd things happen all the time; when someone sees somethings strange, why do they just shake their heads like they think they are crazy?

I have recently started getting into Dr. Who and Torchwood and I notice this happens a lot, as well as often in other universes. Someone sees something strange out of the corner of their eye, or even directly look and/or speak to them, will ask someone else if they can see it and they don't know what they are talking about. That same thing will end up coming back to bite them in the ass.

With all kinds of aliens around, why would they think their partners would think differently of them for seeing something they could not?

Also shouldn't these people who have to deal with this all the time be less likely to think they are just seeing things?
gpt
Just because you regularly run into Aliens and demons and whatnot doesn't mean that everything is out to get you. That's just regular old paranoia.

A better question is why is there always a character who, despite seeing this crazy shit day after day, keeps being cynical and assuming none of its true. Come on Scully, after solving dozens of cases where the answer was "Aliens did it", you right throw Mulder a bone the next time he suggests Aliens did it.