I think this is a lot more common than any other reason.
There is constantly a group of people somewhere shouting loudly that this fact you were just told is no longer true. About everything.
The philosophy of fact and truth eventually has to bridge a gap of trust from the individual. That's where it can be exploited by some group who stands to benefit or worn down by seeing the scientists rewrite the textbooks with XYZ new discovery.
It is nuts. It goes to show how far science goes proving things through deductions rather than direct observation. So much science is done that way.
I think that there would be some infinite energy glitches if it was actually true that light was faster 1 direction than another, so I think the assumption is a good one. But still fun facts