They aren't meant to inforce
The PCI standards council only maintain the standards, enforcement of them is down to the Card schema's and the acquiring banks.
Previous to the PCI standards councils, each card schema (visa, mastercard, Amex) had their own requirements and standards which would have been impossible for a retailer to adhere to. The PCI DSS is meant to be a common standard for all card schema;'s.
The problem is that the card schema's don't have a direct relationship with the retailers, this is done by the retailers acquiring banks, and because there is no co-operation between the acquirers, then the standards do no get enforced. HSBC are not going to tell their major retail customers to become PCI compliance, because if they do the retailers will just move to Barclays, HBOS, etc.
The only way to enforce PCI compliance would be for the acquires to co-operate and suggest that each a retailer does not met PCI requirements they will had a 1% surcharge added to thier interchange rates, That would make the CFO's at every retailer sit up and take notice.
Please note PCI is not about Chip n Pin it's about securely handling the card numbers and associated information, most PCI requirements are just basic good information security practices, encrypt data, restrict access etc. As somebody with 15 years+ experience of working with major worldwide retailers in information security, it's unfortunate but most retailers will not implement basic security practices because however much they say they value their customers and their customers security, unless there is somebody with a big stick telling them to do it, they aren't interested.