There‘s all kinds of uses for a Raspberry Pi. Not everyone is in it for ideological reasons, and I‘d argue just watching Netflix on it is a valid use case too.
I mean, it's still not very good at it - you will only get lower resolutions, and at this point a Raspberry Pi and storage/power/cases are not cheaper than buying a Fire Stick or a Chromecast which works better for that use case.
Most of the time, your device(s) tell the Chromecast what to play, and the Chromecast plays that on its own. There is integration which tries to sync the UI on the "controlling" device to the playback of the Chromecast but this fails often enough for me that it's clear that (in my case) my phone isn't streaming to the Chromecast directly unless I'm screen mirroring.
Corporate scrip is essentially fine too if all you care about is buying cheese (and you can exchange it for cheese...), but that doesn't mean that it's good or that regular money isn't objectively better.
Preinstalling the plug-in would be an entirely different matter for me, and I'd see the ethical concerns there.