This is the reason why you think he's talking too fast: https://www.psychologytoday.com/us/blog/life-bilingual/201302/why-are-they-talking-so-fast
It's kind of a contextual grammar thing. When a pronoun isn't used, and the sentence is using plural verbs, the implied meaning is something like, "Why does one not speak English?" Or in this case, "Why don't we speak English?" It's kind of a rhetorical phrase, much like how we use the word "you" in English. For example, "You don't do it that way," doesn't necessarily mean you are telling someone not to do it that way, rather it means that it's not the standard way of doing it.
I hope that's helpful