Because they are more than likely counterfeits produced in China. I would be sure not to buy and use them or you could be charged for defrauding the USPS postal system if detected. I cant understand why the USPS does not go after
ebay for this.
ebay is complicit in facilitating this illegal activity, allowing such goods to be sold on their website. I would think that the authorities would use the legal system to stop this illegal activity.
Edit- moved s into proper position in word counterfeits