So it's with some relief (heh heh) that you read of several explanations:
Here are the possibilities: The planners overestimated demand. The crowd was so dense that people couldn't get to them. The crowd chose to use Smithsonian museum restrooms, the better to escape temperatures in the 20s. Or the crowd thought ahead.
The evidence appears to support all those theories, and also to suggest a slight lack of enthusiasm.
Oh, really? Lack of enthusiasm for a porta-potty? What's wrong with these people? At least, lack of enthusiasm seems plausible, along with the other possible explanations, although I'm curious to know what "the crowd thought ahead" actually means. I don't know about you, but I don't see holding it in for hours as real alternative. What I envision, given the inventiveness of the American people, a fact the new president acknowledged in his speech, are numerous personal porta-potties carried in backpacks, satchels, and purses. I leave it to you and your inventiveness to picture how these might work.
But then you discover that in the days before the inaugural sale of Depends adult diapers went up by 20 percent. No, you say. Oh, yes, and it wasn't just an influx of old people coming the DC for the celebration. Several not-old people actually admitted that they were getting ready for the inaugural. So then you get to wondering about how many people in that crowd were actually wearing and using their own personal porta-potties. And that's the point where you realize your life was perfectly complete before you ever even heard about this.