Yeah, it happens -- and hopefully the extent of the damage is losing the motor. It just doesn't make a lot of sense to me (warning - rant). They're building these big fishing platforms today with 6 or 7 outboards hanging off the back. That's a lot of weight and propulsion cantilevered out over the transom. When the boat is pounding through the chop that weight is out at the end of a long beam taking a real beating.
Add to that the engineering problem of making a transom strong enough to take the load while keeping it light. You can't make the transom overly heavy because you're going to add the weight of the motors. Then you've got time to worry about. Nearly all materials degrade over time, and for some of the materials they're using we don't have any real long term data -- we're guessing.
Then you've got the fact that outboards are inherently problematic. You have to sacrifice durability for weight. You have to pack everything into a small package, figure out how to dissipate the heat, deal with corrosion, make it serviceable (or at least one would hope). And of course you lose the use of the transom for anything fun like fishing.
Boat builders love outboards because there's no engine installation to speak of. Outboards make a boat easier to put onto a trailer. Outboards make re-powering a cinch. Outboards keep outboard motor shops in business. They're great for skiffs, inflatables and small sailboats. Offshore??? Maybe in a nice new one from a reputable builder, but other than that I like having the engine where it belongs on a boat.