It's often used to describe:
* A process or task: "The meeting went as smooth as honey, everyone agreed on the plan."
* A surface: "The marble countertop was smooth as honey."
* Someone's voice or speech: "She spoke with a smooth as honey voice, calming everyone down."
* A person's personality: "He's always smooth as honey, never causing any trouble."
The comparison to honey highlights the pleasant and effortless nature of something. Honey is known for its smooth texture and sweetness, which makes it a desirable and enjoyable substance.