[yencabulator]

Well, for one, a separate streaming box would only have access to the video it shows. The central multiplexer sees it all.

[nickburns]

Yeah no, that's exactly what I mean (in context of the parent to which I've replied): streaming devices are likely capturing and phoning home screenshots of their own display output, too.

But yes, a smart TV programmed to do the same is even more unscrupulous given that it can 'spy' on everything it displays, to presumably include the input of connected devices.