Maybe I'm in the minority, but I don't see myself ever using them.
There's no point in using them on normal islands, as there's no risk to just pulling up right next to the island. In order to effectively use them on the volcano islands, you would have to park far away, outside of cannon range. Meaning that if you take the rowboat over and die there's no convenient way to get back to the island.
They are also very awkward to drive. If the rowboat is facing towards the beach then it takes forever to get it turned around back towards your boat. Similarly, it can be very difficult to connect the boat to your ship given how difficult it is to position your self correctly. I've tried using the brakes but it doesn't seem to change how wide the turn radius is.
Finally, the rowboats are way too fragile. I row all the way over to an island and place all my loot on the rowboat to keep my ship safe, but then the rowboat just gets destroyed by the island as soon as a rock or a geyser hits it. And there's no way to repair it with planks. It defeats the point of using a rowboat as now I'm going to have to sail my ship over.
With all of these difficulties, it's easier and takes less time to just get up and close to the volcano islands with your ship, rendering the rowboats useless. The volcanoes give plenty of warning to get the hell out of there. If you leave one person on the ship ready to hightail it you shouldn't have a problem.
In order to make the rowboats practical, Rare should increase their hitpoints or add the ability to repair them with planks, improve their maneuverability, and create some way of spawning at them. Otherwise, I don't see myself ever bothering with them.