Duplicated code bloats a code base and is a breeding ground for defects. It's costly! Code that's hard to understand is hard to modify and extend. It too is costly. There are many more examples of costly software design.
I think we can all agree that poor design incurs costs.
So why do we call poor designs code smells? I've gotten to a point where I find that "cost" is a better term than "smell."
Code Costs. Duplicated code costs. Obscure code costs, etc.
Everyone, no matter if they are technical or non-technical, a maker or a manager, can understand the term, cost. The same is not true for smell. Cost is a ubiquitous word, an idea that a whole team can discuss and manage together.