Steve Jobs called the original Apple TV a "hobby", and, similarly for now there isn't any pressure for it to massively grow.
I love their SciFi material but two seasons of severance in three years won’t keep people subscribed. The only reason I have Apple TV for more than a month or two out of the year is due to the bundle plan math working out with family sharing.
Software support is vital here, you can't just say that if the hardware is good then people would buy it. What good is it if you can't use it?