...There's plenty of room outside the ship's channel for a small vessel to navigate without fear of being hit by a ship...
No, not always:
...AIS? Not so much. The ships all follow the ships channel. The channel is very narrow and is very well marked. There's plenty of room outside the ship's channel for a small vessel to navigate without fear of being hit by a ship. Using this strategy allows you to basically ignore the large ships -- the only ones transmitting an AIS signal -- and concentrate on smaller vessels, buoys, flotsam and jetsam, and sailing your boat. No need to know the names and particulars of the ships passing by. No need to call them on the radio. Just stay the heck out of their way, sail your boat, and pay attention to your own navigation. :-)
Suggesting that someone sailing on a river never enter or cross the channel is like suggesting that someone walking in a city never cross the street. It just isn't reasonable.
It's a funny thing about channels - they tend to go down the middle of the river! So what's left is 1/3-1/2 the width of the river or less. That sliver of water may be OK on a reach or run, but can be dangerously narrow for tacking. And the fact is, most of the time there is no large traffic around, so you can safely cross the channel and use the whole river for tacking.
And even if you stay out of the channel, there are bulkheads and anchorages along much of the river, so the large vessels leave the channel more often than you may realize.
I typically sail about 2 mi downriver from one of those anchorages. With AIS I can tell at a glance whether those vessels are stationary (safe to enter the channel) or starting to move (stay out of the way). I don't need to call them, or look up their name, or pull up any menu for detailed information. I just look to see if there's a 5-minute vector in front of them, and I immediately know how fast they're moving. And since it's all overlaid on a chartplotter screen, it doesn't take any more attention than I'm already paying to the chartplotter (which I need to do if I'm staying out of the channel near shore).
Let's make a deal. I won't make you use that AIS that you like "not so much," and you won't tell me that I should ignore those big ships that come along every couple of hours.