The biggest difference between #SpotifyWrapped and other music services’ end of year recaps is that Spotify compares my listening activity to its other users.
It’s computationally easy to pull a single user’s listening history. That data processing and infographic generation could be done entirely on device.
However, comparing 700+ million users’ listening histories is a takeover-entire-datacenters scale processing job. So Spotify has to do a snapshot of data at some point.