The real question is why Roku turns that on by default. If someone has specifically selected a theme, why would you change that out from under them. I can understand having it defaulted if the device has the default theme and has never changed it. But it’s not nice for Roku to keep pushing themes on someone and expect the user to dig down 3 levels and turn off a default setting.
Not only is this on be default, but it apparently resets itself over time. I came here to complain because I assumed it was not an option to turn it off -- because when I set my TV up two years ago I must have turned it off and forgot. Use it or lose it, and now I have had to use it, again, I will not forget in the future.
As aggravated as I was when I came here, I will give Roku kudos for making this optional.