Adhering to PCI compliance standards ensures the cardholder data is handled in a secure manner that helps reduce the likelihood of sensitive financial account information stolen or hacked. It helps in avoiding fraudulent activity and mitigate data breaches which is critical for gaining customer confidence and trust.
In addition, any vendor working with a service provider using their products or services for accepting card payments or storing/processing/transmitting cardholder data will need to be PCI compliant.