Why are some X2 capacitors not for use "in series"

ElCaron:
Well that cannot be the only thing to it. Why would a manufacturer drive away customers by ruling out certain uses so that no reputable device manufacturer would use it?

Huh? There are perfectly valid uses for a capacitor, you aren't required to connect it to the mains!!

Better not to get class-action lawsuit for starting fires don't you think? Good business practice!