To add to what Hippocampus said about different use patterns, I think the nature of motoring vs sailing also means it's a bit harder to have a simple "oops" that tests the boat's stability limits. If you're pushing a sailboat a bit, even without much sea state, it's not too hard to mess up and put a rail in the water. Not so easy on most powerboats without actual really bad weather or breaking waves in an inlet.
Plus, as long as you remain under power, you have more control over the boat's direction and movement through the waves (provided the crew isn't too worn out to manage the boat effectively or you're on a course autopilot can steer adequately without needing constant throttle changes). So you have a better chance of being able to avoid running broadside to large waves and getting the rolled to a dangerous degree.
As mentioned, crew endurance and comfort is often limiting before the boat is. It's certainly the case on my boat, even with a total lack of stability information available to me.
The worst we've been out in was a rather nasty surprise thunderstorm in weather conditions (and forecast) where we had no reason to expect any. We had light wind and 2 footers just forward of the port beam when we started. Storm popped up and those became 3 footers, then the wind shifted and picked up further. That quickly turned into 3 footers from the original direction and 3 to maybe 4 footers quartering off the port bow. We were already on plane for the sake of roll comfort when it hit. Nudged the throttles back just a hair and kept going at about 15 kts. The ride sucked, but the boat was doing just fine. At low speed it would have been very rolly and the pitching would have been significant on our course, but at 15 kts roll wasn't much of an issue, more just some gentle, well damped tilting motions. We were still pitching a bit, but not pounding or slamming. Lots of spray plus rain, so it wasn't exactly a fun day.
But the boat wasn't a handful at the helm in those conditions or anything. Just a bit of steering to keep us on course and the boat moving reasonably through the wave sets. Once we got to somewhere we could head in (which happened to be our destination anyway), we were able to turn downwind and adjust speed a bit, at which point the ride was fine (save for a disconcerting moment when a nice haystack formed under us and ventilated the port prop for a split second). Didn't rearrange the cabin and didn't splash a drop of water down the engine room vents, which means it all felt worse to us than it really was.