I'm a former Last.FM user. They'd play a mix of past favorites and related recommendations, then adjust based on feedback (e.g. likes). There was a noise slider that would influence the ratio of new songs (and indirectly bring in recommendations from farther away from your core tastes). When I first found out I could be more adventurous, I was very excited, as I (like most people) pride myself on being curious. As it turns out, constantly discovering new songs from unusual genres is exhausting. This turned out to be a feature I very much wanted, but felt unhappy using and disappointed in me not using. Maybe this is common enough that the Spotify PM for Discover Weekly experimented and decided not to ship it.