Because during the Troubadours period, the Church had all the power, and everything that was created or composed, it was absorbed by the Church and credited to it. Beyond this fact, it was not common among the Troubadors the tradition to write their songs, which turn it easy to the Church to keep the songs under its influence.
Explanation:
Troubador's school existed during the High Middle Ages in territories such as Galicia and in some points of Italy. These countries during this period were extremely catholic, and the Church had a tremendous influence on art and culture. Troubador's compositions, one way or another, were credited to the Church because of its influence and power.