The only reason I can think of that anyone would implement something so inane would be to discourage people from dual booting. Or, as an example, to make sure

The only reason I can think of that anyone would implement something so inane would be to discourage people from dual booting. Or, as an example, to make sure that you won't "mod" your Grandma's computer and silently break auto-updates or cause performance issues without her knowing. The screen is clearly designed for non power-users, and Google wants it to look as scary as possible to dissuade consumers who are just following a tutorial online, or something. EDIT: I'm surprised this is controversial. It's one of the express reasons for verified boot warnings.