Because it is God's word or "guidebook" if you must, for us.
2 Timothy 3:15-17 (New King James Version)
and that from childhood you have known the Holy Scriptures, which are able to make you wise for salvation through faith which is in Christ Jesus.
All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work.
This is the most authoritative book, written by God himself. It contains all you need to know about God and what he wants of you. It provides daily living wisdom to things in the future and afterlife. It's the only book that SAVES your soul through the trusting in the main character of the book -- Jesus Christ.
We should read the Bible because it's Gods word. Whatever you can't find in yourself or others you can find in/through Him. Reading Gods word can give you more insight into things that may be confusing like the beginning of the world.
The Bible is used as a foundation for so many different religions around the world it is amazing...
Since the majority of people believe in God & the Bible...
wouldn't it be a good idea to find out what all the fuss is about?