The tokens were typically issued as souvenirs from crypto conferences or other events, and were supposed to function as cryptographically verifiable proof that the owner attended an event. The fact that the POAPs were tradable of course undermined this somewhat, but nevertheless the crypto world had come up a number of reasons why POAPs would be the future of event planning and digital identity and all kinds of things.
Now, the project's co-founder has announced that "Unfortunately, crypto's funding cycles and distribution dynamics made it hard to build a sustainable company without cannibalizing the ethos that made POAP mean something. Building on a fragile and quickly evolving stack, in the middle of an incredible hype cycle, only added to the challenges."