This might be useful for a tiny island. Ship from a large Caribbean island to a small one for example. The distance means the round trip is day (night?) trip, and there a things you want shipped in every day, but airplanes are expensive. I'm sure there are other niches where there is only a small amount of cargo going from point A to point B as well. However in general the world needs more cargo and so this doesn't make sense for most.
I actually think there's an argument to be made for this to be an alternative to typical cargo ship operations.
The challenge when moving goods via ocean vessel is that everything takes _a long_ time. Loading and unloading the vessel can take days. Transit is weeks. Unloading the vessel takes days.
You have 2 options now: air freight which is crazy expensive but gets it there in a few days max or ocean freight which is relatively cheap but might take weeks. If you can cut out vessel loading/unloading you save at least a week.
Maybe they might not be restricted to Long Beach or Port Newark.
Island hopping is a niche where electric flight might get started.
Hawaii is looking at running some next year.
https://www.sfgate.com/hawaii/article/hawaii-electric-airpla...