I live in a city. A cold city for a good chunk of the year. On the worst winter days I'll see about about 1/2 dozen others. I sort of catch the edge of downtown on my way into work. I'd probably see more if I took a different route.

It always surprises me that I'll set several other bikes when it's really cold (-20 or worse) but on a cold, windy, and rainy day there might be only a couple others.

On a nice day in the summer it can be harder to tell who's a commuter and who isn't. I'll usually look for a backpack or pannier. On a particularly popular route I got to well over 100 one day before I lost count. I was maybe half way home. In a bigger city or a European city popular with cyclists that wouldn't be anything, but I found it very encouraging.