Personally I also don't see the niche they serve. If I'm going far away I take a train or a car. I pretty much exclusively use my bike to ride to a nearby grocery store or do other close-by errands. If I'm doing short errands like this, I really prize being able to get on and off quickly and lock my bike up quickly. A device like this needs to be taken with you when you leave your bike to prevent theft. It's a whole nother step and a lot of extra weight
People who already invested in an expensive traditional bike and want to have the option to add electric support to make trips easier and faster without having to deal with selling their current bike and buying an even more expensive e-bike.
There’s also the fact that many people have bike racks that are fine for traditional bikes but not the additional requirements necessary for some (most?) e-bikes such as weight and strength.
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Just because it doesn’t work for you and your specific worldview doesn’t mean others wouldn’t see value in it.
When I read your comment before the article I thought it was some sort of complicated contraption in multiple parts. Instead it seems pretty compact and easy to disengage. I’m not sure what you’re missing in terms of a niche either. Anyone who just wants to ride with less effort but use their existing bike?
Are you elderly, differently able, live in extremely hilly or hot terrain, or only willing to bike if it’s half the current effort?
That plus “already has a bike” is a massive market.