Is it simply that we have become lazy, self involved creatures whose only concern is our comfort?
The answer, of course, is all of the above, and more. To try and parse the totality of human behavior into a sentence is idiotic in the extreme. So is the idea that we could encompass the meaning of any person's sartorial statement in a three word summary.
Things changed when we got to the 20th century. Oh boy, did they!.
And now, in the 21st century, the idea of wearing a special costume that is deemed appropriate only for breakfast or morning is utterly absurd. We get up and into our day, whatever that might be. If it is business, then so be it. If it's yoga class and taking the kids to school, then that is what is real. We think of lounge pants, leggings, snuggies, t shirts and hoodies as at home gear, as well as most of it being clothing we would wear in the outer world.
I have no doubt that there will be one.