This guy bought an internet connected sleep mask so it's not surprising that it was collecting all kinds of data, or that it was doing it insecurely (everyone should expect IoT anything to be a security nightmare) so to me the surprising thing about this is that the company actually bothered to worry about saving bandwidth/power and went through the trouble of using MQTT. Probably not the best choice, and they didn't bother to do it securely, but I'm genuinely impressed that they even tried to be efficient while sucking up people's personal data.
I took an IoT course in school, and one of the things they loved was using protocols like MQTT. I was more or less required to use it on my projects because “that’s how IoT communication works”. So to me, it feels more academic than efficient.
Meanwhile streaming everyone's data, negating any benefit.