In a word? Yes! Our clothing choices reflect the importance we place on an event. Yet Americans have a penchant for comfort that translates into casual clothing, especially outside the workplace. This attitude shows in the way we dress for church. While it is edifying to see a number of people wearing their "Sunday best," more and more people are opting to attend Mass in attire more appropriate for a workout at the gym or a visit to the beach.
It is certainly true that the Lord knows our hearts and that all are welcome in His House, but the choices we make regarding our appearance are a way of providing a witness to our brothers and sisters that worship is important, and that the Church is no ordinary place.