I love black and dress in black or grey almost all of the time, in my "regular" clothes." That said, I only have one piece of black cycling wear (on the top). It's a winter piece, long sleeved, thermal jersey that zips up. It has red and white reflective accents on it. I've only worn it in the day time, in bright sun a couple of times. Most of the time, it's been worn under my screaming yellow jacket. My other jerseys are all kinds of colors.
I too, have noticed many commuters with no lights, or only a horrible reflector at dusk. Most of them are young people or older people, "invisible" cyclists, etc. I see them on my way home from the city I am working in for my internship, which has a large immigrant population. No helmets, either. Going the wrong way. But, I also see this in Cambridge, which has a huge cycling population, commuters, who zip through very heavy traffic, in street clothes, with no lights. Yes, it is brightly lit on the main streets, but I am sure they go into residential areas to get home. Around where I live, most of the commuters have lights, but they could have more/better ones.
When I ride in the dark, I have a bright headlight, a very bright rear blinkie and a blinking ankle band on both legs, as well as a reflective vest. One day, when I was coming home from my before work ride, DH was going to get bagels and saw me, in a pretty dark corner of my neighborhood, He said I was extremely visible, so I guess it works.