I don't think that's it, except in a very general sense. I mean, sure we are overbooked and overtired for the most part, and that does cut down on what we notice, to some degree. But here I don't think it's the noticing so much as the understanding that was the cause of the disconnect.

By that I mean that our culture has changed, and people don't assume dark clothing is for mourning (except specifically at funerals) because out of that context it could mean so many other different things.

For instance, people may have noticed, but lacked the context to think it meant anything more than you weren't able to do laundry two weeks in a row, so you were down to your less favorite or more formal clothes until you had time to rectify that. Alternatively they may have noticed the change, but didn't know how to ask you about it without risking making you or themselves uncomfortable.