In floatplanes and boats, there's no such thing as too much power.
We would never buy a 40 foot boat with two 80 hp motors. Sure, they'll shove the thing along at the typical creep speed for this kind of boat. It it's a displacement boat like a Krogen, then there's a point at which having more power has no value as you're limited by the hull speed.
But most cruisers of the type most of us on this forum own have semi-planing hulls, which means if you have the power you can use it to go faster if you want to.
The boat we have in the PNW, a 1973 Grand Banks, is an eight knot boat because of the engines that are in it which total 240 hp (two 120s). But later versions of the same boat have 440 horsepower (two 220s) and they can be cruised at 10 or 12 knots or even more if one really wants to push it. Same hull as ours, but more power.
A lot of boaters want to get somewhere fairly quickly, cruise around for a week or three at a leisurely pace, and then beat feet home. This lets them get the maximum time in the area they want to cruise around in and spend the minimum time getting there and back. Very important to someone with a limited a mount of time to take a cruise.