The iPod is in terminal decline. Apple’s first new blockbuster product of the 2000s helped reinvigorate the Cupertino tech giant from its 90s era slumber and set it on the path to greatness. But sales of the device that transformed the MP3 player industry have been falling at a rapid pace. They hit their lowest level since 2005 last year and are expected to drop further again in in 2014.

Apple still made $4.4 billion in sales from the product last year, but that was a decline of 21%. Of course, this is not really surprising (and has been noted by others before.) The iPod was completely replaced in terms of functionality by the iPhone years ago. Its biggest market is perhaps parents who don’t want their young children to have phones. There are also people who buy small iPods to use when they’re working out, though smartwatches are now clearly aimed at that use case as well.

The importance of the product can’t be understated though. The biggest legacy of the iPod might be the fact that it helped Apple establish credit card relationships with millions of consumers, who remain locked into Apple’s ecosystem to this day.