You are right on with this - why do people leave switch plates on when it's just so easy to take them off? Another thing that happened to us - we had the popcorn ceiling taken off and the ceiling painted white. When the job was done and I later went to change out all the fixtures/fans, they had left every fixture in place, so there was a large patch of popcorn and unpainted ceiling left behind - it just didn't dawn on me to specify that they take those down before scraping and painting. It was kind of a mess.
Denver House Painters of Colorado