Clearly there are two reasons Christians worship God: because He created us with a heart bent toward worship. It's in our DNA to worship something or someone. The second reason is because we love him, and that love feeds our desire to continue worshipping him. If we don't love God, we won't worship him. It's that simple.
People are going to worship something so if it's not God, it will be something else. I amazing thing about God is that he promises to meet us when we worship. Nothing, or no one else, does that. "He inhabits (is right there in) the praise of his people". So why wouldn't we worship a God like that?
The best definition I can think of for worship is our heart-felt response to someone who we know died to liberate us from the dregs of sin and the chains it wraps us in. We worship him because he did something very great for us. I believe worship is a response to the knowledge of who God is in our personal lives: not what someone else says about him, but what we've come to know and love about him, personally. Your mind can worship just because someone asks you to, but your heart can only worship when you love, deeply.
For my heart to worship an unseen God, I need to know something about him. So, what do I know about him? I know he created every living thing. I know he created us in his image: to look like him. (Gen.1:27-28) I know he is a God of infinite grace who covers my sins. I know he is love. I know every good and every perfect gift comes down from God and in him there is no changing or turning aside from that. I know he inhabits the praise of his people. I know we are his workmanship (he fashions and molds us) and I know he ordained us to walk in good works. (Eph. 2:10).
Having that knowledge what do I do with it? If I really believe it, my heart can't help but worship him.
Ps 100:4-5 says, "Enter into his gates with thanksgiving, and into his courts with praise: be thankful unto him, and bless his name. For the Lord is good; his mercy is everlasting; and his truth endures to all generations". That kind of praise comes from the heart.
There are many ways and forms of worship, but they all are inspired by love in your heart. Worship may be in a church building, or it may be felt sitting in a deer stand or fishing on a river bank. Where we worship doesn't matter, but worship will always be initiated by gratitude toward someone bigger than we are. That's something you feel in your heart. I can praise him with my lips, but for my heart to worship, I must love and that satisfies the part of me that's created to worship.
You are God's art work. You are special to him. Psalm 139 says he had a purpose for you from the beginning. When I sit down to paint a picture, I always have a preconceived idea of what I want the picture to look like when I am finished. I think God did the same when he created us. From the beginning of time, he knew what he wanted us to look like. He knew what he wanted us to accomplish and do on this earth. Do we always do what he preconceived? I don't think so. Sometimes, my painting doesn't turn out exactly like I want it to, but I don't get mad and throw it in the trash. What I do is keep working on it until I'm satisfied with it. I believe God does the same in us. He continues pushing and prodding us toward his intended goal.
Why do we worship? Because we believe. It's that simple. Psalm 106:12 "Then believed they his words; they sang his praise."