The larynx allows us to firmly shut off our airway (far better than lips alone) in both directions (unlike the epiglottis that just prevents inhalation).
By firmly shutting off our airway, we can stiffen our bodies to facilitate lifting.
The larynx is also a secondary safeguard against things getting past the epiglottis.
I'd find it interesting for any language as it'd probably work just as well for people without a voice box - kind of makes you wonder why we evolved one. Speed?