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.
The Lead Renovation, Repair and Painting (RRP) Rule establishes requirements for firms and individuals performing renovations, and affects contractors, property managers, and others who disturb painted surfaces. It applies to work in houses, apartments, and child-occupied facilities (such as schools and day-care centers) built before 1978. It includes pre-renovation education requirements as well as training, firm certification, and work practice requirements.