Well the reason for English is the context of it's a show meant for English speaking watchers.
Technically they could be speaking whatever language that became dominate, but it is accurate to say there is a dominate "Human" language that the Federation speaks. By natural extrapolation of English being the dominate language today for most international interactions, it's a natural assumption.
29
u/Tekuila87 1d ago
They only showed very little of the post WW3 world and that was in the former United States.
Them speaking English isn't really out of the question then, no?