Nobody's locked-down personal pocket computer needs to be involved at all for this most mundane task.
Simplicity.
The only thing is that if you set up with all HomePods you can have your TV audio go to them too in stereo. Very cool. And Google doesn’t have that feature.
Can my neighbor not stop by and watch some TV with me and have the ability to pause it?
I might as well publish the SSID and passphrase on a billboard, or just go full Bruce Schneier and leave it open for all.
(Or.... You know, a real remote! With real buttons!)
The original argument was in favor of the OG Chromecast's method, wherein: There is no dedicated remote laying around that anyone can pick up and unambiguously make work.
It is good to have options.
(And modern Google-produced streaming devices, whether they are good or bad, do provide options.)