The simple answer is that I don't like Spotify as much as I like GPM and Tidal. Tidal is my go-to for high-quality music when I'm listening at home on my nice speakers. I've found that Tidal has the best radio experience, at least for the type of music I listen to (Spotify and GPM have a bad habit of playing the same exact songs / artists when I do a radio for a particular artist/album/song, Tidal varies it more).

Google play music is simply extremely convenient considering how nicely it works with Google Assistant. Additionally, I have tens of thousands of my own music collection uploaded to GPM that I'm free to download whenever I want without restriction. Spotify lets you play music offline, but it's basically cached and still tied to your premium Spotify subscription.