I'm usually aware, as I ride around town on my bike, of places where other bicyclists congregate ... or at least where a lot of bicycles park. There's a restaurant that has bikes locked to the fence all year long. There's a coffee house where it's hard to find bike parking in the summer. And the museum of nature and science, about a mile from our house, almost always has quite a few adult and kid bikes parked outside when the weather's nice.
Because I look for bikes parked together, and because I knew it was bike to work day, on my way around town that day, I was naturally keeping my eyes open for places where people on bicycles were congregating. The breakfast stations, naturally, were good places to look, and the hundreds of bikes tagged and parked securely at the bike home from work event was fun.
As I was riding to do what I could to help set up for the first event, having left the house at 5:40 (which is entirely too early, unless there's mountain adventure on the agenda), I saw from a block away probably 15 or 20 bikes parked on the sidewalk. It wasn't 'til I got closer that I realized it wasn't a bike to work day event ~ it was the temp work agency. I ride to work because it's environmentally responsible, because I can stay a little fitter, because I like to be active. But if I 'need' to, I can drive to the office, or anywhere else for that matter.
For these guys, every day is bike to work day (if they happen to get work that day). Every day is 'get up at 4:30' day. They ride because they probably don't have a car, or because their family needs the car that day, or because they'd rather feed their children than spend the money on gasoline. They would probably rather drive, since their work (if they get any) will be plenty physical.
So let me get off of my high horse and remember that most of the world doesn't have access to the luxuries that my life affords me. For most of the world, to have a bicycle as transportation (especially to have one that is complete and works well) is a luxury.
Sure, we can be a big visible presence one day a year (when the weather will probably be nice). But let's not forget the people who have to bike to work every day, through all kinds of weather.