"When I was young, I went to Mass because I had to. Now, I go to Mass because I want to."
It is rare these days to hear a pastor declare, "You must go to Mass." Actually, it is rare these days to hear a pastor declare that you must do just about anything.
Sometimes the phrasing is softened for contemporary sensibilities: "We are to do what God has asked of us." We "invite" our fellow Catholics to do this-or-that. Sometimes a prophetic or vocational dimension is highlighted: "We are called to act with justice, we are called to love tenderly." (I have daydreamed about taking this popular hymn and rewriting it for the First Precept of the Church: "We are called to Mass on Sundays, we are called to cease laboring...")
It is not that priests consider Sunday Mass to be unimportant. The Eucharist is all-important to most every priest. However, the element of obligation strikes many priests as well as their parishioners as an outdated and immature notion, as something more fitting for children than for adults, a view of Christian discipleship that is contrary to the God-given freedom to choose whether and how to worship God.
Still, is it not "right" to give Him thanks and praise? And if, indeed, we are called to "act with justice," is it not an act of justice toward God -- who has created us, redeemed us, and sanctified us -- that we offer Him fitting worship? There are many obligations in life -- fidelity to one's spouse, for example -- which need not stunt a mature, free, and sincere self-offering.
There is no good reason why we cannot, or should not, worship God both because we wish to and because we ought to.