The grass is wet because it rained last night. This seems the simplest and most elegant expression of the meaning. I am always suspicious of "reason (s)" and "why" being next to each other.

Understanding the Context

There can. Why is used here as an interjection. According to Merriam-Webster: —used to express mild surprise, hesitation, approval, disapproval, or impatience <why, here's what I was looking for> In my. Jan 16, 2011 · Why have a letter in a word when it’s silent in pronunciation, like the b in debt?

Key Insights

Can anyone please clarify my uncertainty here?