As a child, I was raised to wear nice clothes whenever we went out, and especially for church or sunday school. Mom wouldn't let me wear shorts to school when it became the norm when I was in junior high, and it was a battle to get to wear jeans (my sister got the worse battle of that, as she's ten years older and was into bucking the norms as a rebellious teen in the late 60s).
When I was 20, I was briefly engaged to a man who was a practicing Catholic and he took me to mass, and I was mildly shocked to see how many people were wearing jeans and sneakers to church. So already a different norm had shown itself to me.
To this day, I remain a person who is far more comfortable slightly overdressed than underdressed. I was mortified once years ago when my husband told me not to bring anything special for an event we attended in NYC. I wore a silk blouse and jeans with heels, and all the other women were in fancy cocktail dresses, and I kind of wanted to die.
I tend to believe that most people are doing the best they can. Some people don't care, and honestly, how someone else dresses doesn't hurt me, so why care? But I personally I prefer to dress in a way that shows respect for my surroundings, the occasion, and anyone who may be honored at such a gathering.