Why?
“Never, never, never, never give up.” Winston Churchill
You’ve learned hiragana. That means it’s time to do something with it and learn your first bit of grammar. You’re learning about です in this chapter, and the reason you’re learning it is because it will lead to several other grammar points you can learn, like か, でした, じゃありません, and じゃありませんでした (don’t worry if you don’t know what these are yet, you aren’t supposed to). です also allows you to work with nouns and make very simple sentences… sentences that will grow into bigger more complicated sentences and eventually turn into something that will help you to learn adjectives and verb grammar patterns as well. です is kind of like the mother of all Japanese grammar points. Learn this, and you’ll open doors to almost anything and everything else.