Weddings and Attire

I was at a wedding this past weekend and can't wait to tell you some of the interesting things that happened! One of the major things that noticed, is the dress attire of the guests.
Moms and dads spent a lot of money on their clothes, the wedding party was formal, (it was a 4 o'clock wedding --very formal), the ushers were dressed up---why weren't the guests?
Out of 210 guests, I counted 5--yes, 5! women that were dressed up very well and looked great.
Everyone else had on jeans, short shorts (Yes, khaki short shorts!), backward baseball caps, and t-shirts that had seen better days.
I was totally appalled by the lack of respect for the bridal party. Apparently their friends don't think very much of them not to mention not caring about themselves.

When did it become the norm to dress down at a wedding?