Causal writers who do not know how to insert • may be confused when editing someone else’s unicode bullet list.
* + and - are all easily accessible from a standard keyboard. Pressing Option+8 on the Mac to insert an additional • list item is not intuitive. If the writer does not know the key combination then they must use copy/paste, search for how to insert •, or rewrite all of the existing list markers.
No other Markdown syntax requires knowledge of key combinations (besides Shift of course).