Right, Sparks is sitting in the control room, driving the boat. They've reduced crew so tightly, he's driving the boat, monitoring all the radios, AND serving up meals at the same time. Right.
It's not a matter of not having enough crew. It's a matter of not having a crewman assigned to the duty of conversing with recreational sailboats, because there is no need to perform such a duty. Also, as GeorgeDog pointed out, in the case of a sub there are only two or three people who can even see any other boats, and they are busy guiding their own boat.
As an aside, in a former life I flew military aircraft. Virtually all civilian aviation communicates on VHF radio, while virtually all military aviation (at least in my corner of that world) communicates on UHF radio. More than once I operated out of busy civilian airports alongside large commercial aircraft, without even being in the same band on our radios. And you know what? Both we and they were able to safely do our jobs quite nicely.