Why Do Some Songs Do Well on Spotify but Not on YouTube?
Spotify and YouTube are completely different types of services. YouTube tends to be more for discovery and finding new music that you enjoy, but Spotify tends to be for playlists and consistent listening. There are strong trends between discovering new music on YouTube and then fans consistently listening to that same track in their Spotify accounts.
Additionally, fans can listen to Spotify without requiring a tab to be open, viewing to be active, or screen to be on via a mobile phone.