Just read Macrumors buying guide—
“Without an Apple Music subscription, HomePod is able to play content that's been purchased from iTunes along with Beats 1 radio content and podcasts. HomePod will only be able to play content that's been directly purchased using iTunes, rather than any music in an iTunes library.”
And that is the reason I will not be buying a HomePod. I decide what music to play and what the source is. Not Apple. Intentionally limiting who I can use as a music source is a guaranteed way of getting me to ignore your product.
Fail. Why spend this much cash on a great piece of hardware only to be tied to a single ecosystem? I don't think anyone would put up with an iPhone or Macbook that only ran Apple apps/programs. No Office, no Google Maps, no Spotify, only Apple Music, Apple Maps, and Keynote. Who would go for this?
Yet this is exactly what Apple is proposing with HomePod. Hmm...