Sorry. You are absolutely correct about the DRM. I completely overlooked that one. But that is in this case just "convenient" for these app makers.
I am still right as well and this is also why you can't use it though apple Carplay or Android Auto even though your phone might have the correct DRM files/certificates. Because they don't want idiots to do this.
And I know that you can use Netflix and others through Apple CarPlay on a jailbreaked iphone and on rooted Android phones via Android Auto, but NOT directly on "correctly configured" devices for the obvious reasons that those companies don't want you to do this.
Netflix is even working on an update (not official) to enable "audio only" mode (podcasts, standup comedians, etc.) though Apple CarPlay and Android Auto, exactly to prevent idiots watching the screen while driving. Better implement this audio feature and allow audio only, then having idiots trying everything to use Netflix in the car. Or Disney+ for that matter.