The inventor of the dress code, I would say, was the French king Louis XIV. To be received by him, and he insisted on that, you had to wear a hat. He died in 1715, presumably wearing his hat. Since then people have slowly learned, mostly from their mothers, what to wear or not to wear, according to the occasion. That is why, until recently, people never showed up at five o’clock tea clad in shorts and wearing flip flop sandals without socks. But they do now. They also go to a symphony concert or to the opera in the same clothes they had worn in the morning to take out the trash. Restaurants and cruise ships still hang on to the code but they cannot enforce it. After all, those people are the customers. They bring in the money. In other words, the dress code concept is defunct. R.I.P.
Strange as it may sound, I have noticed that there is also an unwritten un-dress code. That code is universally recognized and, unlike the dress code, is strictly adhered to by all. One never sees people at a concert wearing just their underpants. But, come to think of it, I have noticed that bathing suits 
get smaller and smaller with each annual Sports Illustrated edition. Could it be that the un-dress code is also on the way out? Maybe I should make an effort to get rid of my excess tummy. This could become embarrassing.