Every great story begins with "Once upon a time..." (stated or implied)
This is what a song's intro says: "Once upon a time." It sets the stage for what comes next. It draws your listeners in. Intrigues them. Gets their attention.
A master storyteller knows that the "Once upon a time" is vitally important. Vibrant, compelling, and entrancing.
It's the same thing with the introduction you play. Make it count (even if it's just one chord.)