Folks insinuate that outrunning bad weather is a uncommon thing, but in fact it is not. We outrun bad weather frequently. Not deadly bad weather, I'm a better captain than that, but uncomfortable weather, or better yet lets say unfavorable weather is easily avoided. For example we get a strong sea breeze in the late afternoon. This makes inbound docking much less fun. Going fast a bit to avoid that is an option.
Another advantage of large engines is the ability to smooth out the boats ride. In any kind of sea boats rock. It doesn't have to be a big sea at all to create significant rocking motion. Well, apply some power, and the boats stern pushes down in the water a bit. This greatly reduces the rocking motion.
Another use is getting across a wavy section of ocean quicker. At 8 knots my 35 mile crossing is 4 1/2 hours. At 15 knots the same crossing is 2 hrs 20 minutes.
Yet another use of power is actually getting somewhere by a certain time. I live four hours from the boat. After grocery shopping, etc, and prep time we are generally ready to leave the dock at around 4 pm. Our favorite cruising grounds are around 65 NM away, and dusk is at around 10 pm. Getting after it part of the way puts us setting anchor in time to take the dogs to shore for their last potty break during daylight hours.
So, while approx 75% of our engine hours are at displacement speeds, the 25% of the time we spend at a fast cruise sure comes in handy, for a variety of reasons.