It serves the token holder if said party just declares the ticket or other item a forgery or otherwise invalid, and doesn't let you in the venue or locks your a

It serves the token holder if said party just declares the ticket or other item a forgery or otherwise invalid, and doesn't let you in the venue or locks your account. It also serves the holder if they want a safe secondary market to resell or trade tokens. So basically, decentralisation doesn't serve the vendor, only the consumer.