Society is growing more and more casual. Most people put little thought into dressing for Mass - perhaps you have heard: "Come as you are! God doesn't care what clothes you wear. He just wants you! Of course God loves you just as you are—that's the only "you" that exists!".
However, the more I reflect, the more sure I am that what you wear matters. This is the case in every other meaningful area of life. When you dress for a funeral you dress to show mourning. When you're going out on a date, you dress to impress someone.
In fact, it's hard to think of anything people will dress up for anymore. This bothers me because how we dress acts as a sign of how much respect we have for ourselves and for other people. If we don't dress up for anyone or anything, it's a sure sign that we don't respect anyone or anything.
Even if you don't think dressing sharp is worth it for every-day activities, there is one place you should never slum it: Holy Mass.
How you dress for mass matters. There are at least two reasons why. First, because of what it says to others. Dressing nicely communicates respect and honor. When you dress specially for Mass, you're telling God, "You are worth the effort; you deserve my best." It tells your fellow worshippers, "I take Mass seriously; it's not just one casual event among many for me."
Second, dressing respectfully changes your interior orientation. You've found that when you pull on a suit and tie, your thoughts, speech, and general approach to the world all change. You become more gentlemanly. You are more serious than silly. You are better able to focus, display reverence, and sink into prayer. That's why You are convinced dressing up is a spiritual discipline.
Fr. Antonius David Tristianto, O.Carm.