If your Parish Priest wears jeans, sweaters, or any non clerical gear - show him this article!
Following on from my post regarding priestly garb, H/T to Roman Catholic Vocations http://romancatholicvocations.blogspot.com/ for the article below which deals far more learnedly with the subject than I ever could.
Photo at left: Pope John Paul II after his ordination to the Priesthood
5. The Roman collar prevents “mixed messages”; other people will recognize the priest’s intentions when he finds himself in what might appear to be compromising circumstances. Let’s suppose that a priest is required to make pastoral visits to different apartment houses in an area where drug dealing or prostitution is prevalent. The Roman collar sends a clear message to everyone that the priest has come to minister to the sick and needy in Christ’s name. Idle speculation might be triggered by a priest known to neighborhood residents visiting various apartment houses dressed as a layman.
Msgr. Charles M. Mangan & Father Gerald E. Murray. “Why a priest should wear his Roman collar.” Homiletic & Pastoral Review (June, 1995).