I would say a reason to limit the attention paid to it. If some crank came to me with a perpetual motion machine I might take 2 minutes to ask them, "So how does this account for the conservation of energy?" If their first response is "Energy conservation doesn't apply at the QUANTUM level." then I can quickly move on and ignore them. If their first response is "I think it is extracting energy from the Earth's rotation through interaction with it's magnetic field." then it may be worth me investing another 5 minutes to see what the next level of reasoning says.