I remember, when I was growing up, there was an annoucement at every Mass during the summer months, about appropriate dress for church. People would show up in tank tops and short shorts. The church did not have A/C at the time, so I guess they were just being practical, but it didn't "look" right.
I also remember my dad getting dressed up to fly. Jacket and tie on the airplane even if we were going on vacation. People kept mistaking him for a business traveler.
I'm not saying we should return to the days of always wearing a jacket and tie at the office, women should wear skirts rather than pants, etc. I wear pants most of the time (though on Friday I wore a dress). But I don't believe that T-shirts and jeans have any place at a concert hall, upscale restaurant, or religious service (unless you are unfortunate enough not to own anything else).