soundproofing
Speaking of cab vents, they have been around for years, back before airbags, the purpose is so your HVAC has somehwere for the air to go when your not using "Max" A/C where it recirculates the air. Before they were putting them in the back of the cabs they were in the doors and ultimately the air came out the gaps between the frame and door, later they found it made for less road/wind noise to put them in in the back of the cab.


