Why is this the answer?

The answer is wine because this clever riddle describes the different stages of a special fruit as it grows up and changes, eventually becoming the drink we call wine. First, let us look at the beginning of the riddle. It says, "When young, I am sweet in the sun." This clue is pointing to the very start of the process, which is the grape. Before any wine is made, it begins as tiny, sweet grapes growing on a vine out in the sunshine. The sun is very important because it helps the grapes ripen and become very sugary and delicious. These young, sunny grapes are the sweet beginning, just like the riddle promises. Next, the middle part of the riddle gives us a clue that says, "When middle-aged, I make you gay." This is a tricky part because the word "gay" has an older meaning that means being happy, cheerful, or feeling very merry. When grown-ups enjoy wine, especially when they are sharing a meal or celebrating something important, it can make them feel relaxed, friendly, and cheerful. This part of the riddle describes the wine when it is ready to be poured into a glass. It is "middle-aged" because it is no longer a grape, but it is not yet very old. Finally, the riddle finishes with, "When old, I am valued more than ever." This is the perfect clue for very special wine that has been kept in a bottle for many, many years. Think of it like a treasure. Unlike most things, some fine wines actually taste better and become much more special and more expensive the longer they age in a cool, dark place. This aged wine is a rare find and is "valued more than ever" by collectors. This riddle is a very smart puzzle because it uses simple clues about three moments in time, which all lead to one answer. It follows the entire life story of the grape from a sweet fruit to a cheerful drink and finally to a valuable, old treasure. The three stages perfectly describe the life cycle of wine.