There's the good ol' bait-and-switch of tech industry you have to consider. New tech is promoted by emphasizing (and sometimes overstating) the humane aspects, the hypothetical applications for the benefit of the user and the society at large. In reality, these capabilities turn out to be mediocre, and those humane applications never manifest - there is no business in them. We always end up with a shitty version that's mostly useful for the most motivated players: the ones with money, that will use those tools to make even more money off the users.
It's true with all new tech these days, and I'd be doubly worried when it comes to things like emotion detection. There are no good uses with strong business cases, but plenty of nefarious ones.