Leslie Eskildsen - except the fact that some showing instructions insists on shutting off all the lights. Otherwise, sure, don't just touch anything at the showings.
Leslie, it is for that reason that I will make a second key and keep it in the car with me to help a client or even a showing agent that locked the original key in the house.
When I find exterior doors unlocked, I call the Listing Agent for advice... unless I have been told that "the Seller will be at the neighbor's house while you are showing", or similar. I am hesitant to leave an unattended house unlocked.
Leslie - It's hard to know what was locked, unlocked, or on/off in a home. I find it helpful if I place specific "Showing Sign Instructions" by light switches, critical door locks, and other showing information so a buyers' agent and their buyers know how to leave a home for the seller, and what to double check so the property is left the way the seller wants it to be left in.
So True. Just the other day I checked in on one of my vacant listings only to find almost every fan and light on not to mention the back door was completely unlocked as well as the side entry from the outside into the garage!