Physical goods might be delivered to an address outside of the UK (such as Russia or Nigeria) making them difficult to trace (especially if the purchaser used an 'accommodation address').
Electronic goods (such as software) can be downloaded. If the purchaser uses an anonymising service (such as a virtual private network, or simply connecting to the internet through an anonymous proxy server) the recipient can't be traced.
Further, there are money transfer serices whereby someone can easily gain a rechargeable debit card (posted to an accommodation address, so that the recipient can't be traced) and then top it up (either from a legitimate card, or from a stolen one) online. That rechargeable card can then be used at any ATM throughout the world to withdra cash.
Lastly, Bitcoins can be purchased, and later sold on, totally anonymously.
If I can can immediately give you four ways that credit cards can be fraudulently used online, just think of how many additional ways the thieves might well know!