I don’t even think it’s dumbing down. Speed is relative. That’s just how you’d say it when you’re describing your acceleration relative to another body, spaceship, whatever. No one thinks or cares about your absolute velocity on a universal scale.

For the same reason we describe speed relative to the ground on earth. Nobody’s specifying that we’re traveling ~1,624km/hr west, and ~1724km/hr east, they’re just going 50km/hr