And he said to Him, "All these things I will give You if You will fall down and worship me." Then Jesus said to him, "Away with you, Satan! For it is written, 'You shall worship the Lord your God, and Him only you shall serve.'" - Matthew 4:9-10 NKJV
These verses clearly tell us the most basic reason why we must worship God: Because He commands it! He not only commands us to worship Him, but to worship ONLY Him. Satan tells Jesus here that if He will worship him, he will give Him all things. Satan does the same thing to us today. Society has become obsessed with, even to the point of worshiping, the things of this world, money and possessions. We have to come to the understanding that these wordly possessions mean nothing and that God will provide us with everything we need. We must be like Jesus and say "Away with you Satan! I am going to worship God and only God!"