For quite some time, partials were a popular way to share a chunk of HTML as all the developer had to do was to extract the HTML into a file, and then call {{partial}}
where they want it to be included.
No need to fuss about with passing arguments and callbacks.
However, this very fact also makes partials a liability for your codebase. The more you use partials, especially if nested, the harder it is to inspect your templates and data-flow just by reading your templates. Changes are hard to make because you are never sure if a property might be used somewhere in the partial.