So, why do I remain a Catholic? The question presumes that the alternative is the expected choice, as "What are you doing here?" implies that one's presence is a surprise. But in an age increasingly divorced from the mind of the Church, a Catholic could expect this question as much as a man wearing a toga who isn't in a frat house could expect to be asked "Why are you wearing that?"
But when anyone leaves the Church, I imagine Christ turns to each of us and asks us as he did his apostles in John 6: "Will you leave also?" And I answer with Peter: "Lord, to whom shall we go? You have the words of eternal life."
If I am asked why I remain Catholic, I ask in response, what's the alternative? A version of Protestantism that has unmoored itself from the anchor of Tradition and splintered on the rocks of private judgment? An Eastern religion that is philosophically unsatisfying? A vague religiosity that chooses randomly from different traditions and results in spiritual stomach ache? A scientific materialism that cannot answer the most fundamental questions? A hedonistic secularism that simply moves from one sense pleasure to another in between periods of existential doubt? No thanks.
But it's not simply that the alternatives leave something to be desired. It's that what I have in the Catholic faith is satisfying in the deepest sense. Aristotle says that all men by nature desire to know, and in the Catholic faith we have the fullness of truth. St. Augustine says are restless hearts rest only in God, and in the Catholic Church I am united with God in the Eucharist. I have the beauty of cathedrals and the soundness of moral teaching and the true charity of service to others. I have the forgiveness of my sins and the gift of God's friendship communicated in tangible, human signs. What more could I ask for? What more could I want? Where else would I go?