Poop, poop, and more poop!

I took Scooby out twice this morning. Once at 8:45 and she didn't go at all. I took her again at 10:15 and she peed. We came back in the house, I went into the other room for just a moment, and when I came back she had pooped on the carpet.

Here's what I don't understand:

1. Why didn't she poop when we were outside?
2. Why can't she poop on the %#@#$ tile in the den instead of on my hand-knotted, tres expensive rug?

The funny thing is that I knew right away she had done something just by how she looked. I just don't get it.