Why do pipes explode in the south, but not up north?

I was born an raised in Texas, then spent 5 years living in Idaho. I remember the (drip your faucets) training from my childhood, but they never used to run the faucets up North. We did wrap the outdoor pipes but that was about it. My house is well insulated, and my pipes are for the most part in the slab. My neighbors are the same, yet he had a pipe burst. I have been following the local advice and running my faucets when the temp is under 30 degrees or so. What is the deal with that. Freezing is freezing right? Why would it not have the same effect? Anyone got an answer!