Truck drivers need to be able to communicate on the road, but they also need to be safe. To strike a balance, the Federal Motor Carrier Safety Administration (FMCSA) banned most cellphone use, but they did allow drivers to use hands-free devices in most cases.
Like car accidents, most boat accidents could be prevented. The problem is just that one of the operators involved makes a mistake and causes a crash. There are outside factors that contribute -- storms, rogue waves, etc. -- but it could be argued that even some of these accidents could have been prevented if the operators knew what warning signs to look out for.
If a truck driver falls asleep at the wheel, you now have an 80,000-pound vehicle that is completely out of control. That puts everyone at risk in a heartbeat; even just nodding off for a second can be enough to cause a deadly accident. For that matter, even a tired driver can cause a serious crash without completely falling asleep at all.