I think it's a combination of several factors, all mentioned previously by other posters.

Conventions of dress are not commonly adhered to anymore in most places. At one time, knowing the time of day for an event automatically dictated the level of dress. Now, the level of dress is often dictated by the event, regardless of time of day. Couple this with the "dressing down" of the average person, and you have confusion and chaos, as well as discussion amongst folks who actually do know the conventions of dress.

Secondly, and related to the "dressing down" of most people and societal expectations, we are often tempted to "gild the lily" when any level of formal dress is called for because it is out of the everyday norm for us.

Just as an example, I wear worn out blue jeans and old tee-shirts to work. I work in a factory (machinist) and this is appropriate since I dont want to ruin better clothes with coolant and oil. I wear them when I leave the house and take them off when I get home. There as a time, however, when it was normal for a man to wear much better clothes to work, sometimes even a suit and tie, and change into suitable work clothes in the locker room. So, my Monday - Friday wardrobe consists of items that would be discarded as unserviceable by a thrift shop. Saturdays usually finds me in a pair of khakis and polo shirt or indigo dyed (dark blue) jeans and polo or button down shirt. Sundays is a suit and tie. None of these modes of dress approach what would be considered formal black tie, much less white tie. When the opportunity arises, then, there is a definate temptation or percieved need to overdo it.

My humble opinion, submitted for review, and possibly well deserved rebuke!