Why is this the answer?

The answer is birthday because this clever riddle uses a fun and slightly tricky way to talk about the passing of time, which everyone experiences. A birthday is a special day that happens only once every year. It is a time for cake, presents, and celebrating how much you have grown since the last year. Let us look at the first clue: "You get many of me, but never enough." Think about how everyone loves their birthday. People always wish they could have them more often, or that time would slow down so they could enjoy being a kid longer. No matter how many birthdays you have, it always feels like they fly by, and you always want more of them. The clue "You may have one of me but one day a year" is the most straightforward clue. Your birthday is a day you look forward to, and it is a special count of all your years. It always comes just one time between January and December. Every year that passes gives you a new birthday to celebrate. Now for the last part, which is a little more serious: "After the last one, your life soon will snuff. When the last one is gone, your life disappears." This clue is a little bit like a mystery. It means that when a person's life ends, they will stop having birthdays forever. The "last one" is the very last birthday a person celebrates while they are alive. Once that day passes, there will never be another one for them. It is a gentle way of saying that birthdays measure all the time we have in our lives, from the very beginning until the very end. The riddle uses this one simple word, birthday, to talk about a whole lifetime in just a few lines.