I'm Lucky this is what the praise in worship in my church look like. Not quite on this scale, but 400 or so people. It always wakes me up and prepares me for the sermon. 1. THE BIBLE SAYS TO DO IT!!!
Psalms 134:2-NIV Lift up your hands in the sanctuary and praise the LORD.
Lamentations 3:41-NIV Let us lift up our hearts and our hands to God in heaven
Even if it doesn't make sense to us otherwise, the Bible says to do it so we might as well do it.