In no particular order.
To worship Him.
To worship Him along with others who love Him.
He commands it.
To hear the Word preached and thus to know the Lord and His Word more in our lives.
To be spurred on and to spur each other on to good works - prepared for us from before the beginning of the world
To grow in Him - and therefore, in sanctification and in His peace etc
OK, good answer. Thank you.