Sonos
Before the HomePod, other smart speakers like Google Home, Amazon's Echo, and the Sonos One were playing music from Spotify, Google Music, Pandora, Amazon Prime Music, and other streaming services. The HomePod is the first to let you control Apple Music with your voice, but that's it.
If you don't use Apple Music, there is no reason to buy a HomePod.
The HomePod does seem to have one thing going for it: I haven't heard it myself, but the HomePod supposedly has the best sound out of any other smart speaker. But what's the point of a great-sounding smart speaker if you don't use the smart part? You might as well just buy a great regular speaker if you use something like Spotify - or, better yet, a smart speaker that can control Spotify with your voice, like, say, the Sonos One.
Here are all the reasons you should consider the Sonos One instead of Apple's HomePod: