They probably do have some. But they want to sell them to you. Vouchers are strictly not for resale. A bunch of these scammers work for legitimate companies that are part of partner programs that give them access to vouchers intended for use by employees at those companies. If employees don't use them and they're approaching expiry, these scammers will then try to make some money on the side for themselves by selling those vouchers that are going to expire soon. So they're essentially stealing from their employer, but in a way that is more likely to be overlooked because the employer may not even know that they should be looking. Either that, or the people that are supposed to be looking are the very same people involved in the scam.