This is top of mind for me, as I just had to "rescue" a tenant after a showing, as the showing agent didn't heed the showing instructions and he locked the garage door.
Now, I have many homeowners/tenants who simply access their house via the garage door, and hence, they do not lock the door leading from the garage into the house.
I'm aware, this is a safety issue as well, however, it's a lifestyle issue first and foremost.
When I'm showing property, I check all the doors, and if someone else opens a door, I ask them if that door was locked or not; the only house I lock all the doors on is a vacant house.
Please be conscientious as to what is locked or not locked, and remember, you are not the one who lives there, so you should leave it the way you found it!