The iPod has been officially discontinued just a few months shy of its 21st birthday. The iPod, much like the iPad, was something that you really couldn’t appreciate unless you tried it. After that you had to have one.
The success of the iPod is most certainly thanks to Apple retail stores that started opening around the time the iPod was introduced. In the early days iPods only worked with Firewire equipped Macs – so they likely sold a lot of Macs around that time too.
The last iPod is the 7th Generation iPod Touch that I reviewed back when it was released in 2019. You can watch the review here.