All the reasons that you can think of why low-level robots are built fall into two main categories: safety and efficiency. Robots can do repetitive tasks like screwing on bolts and screws all day without sacrificing efficiency and perform dangerous tasks like going under freezing water to locate a wreck without safety concerns if human divers did the job.
Industries like manufacturing have already made robotics part of their process and have dramatically increased their output while reducing their rate of accidents. With this, you would think that the construction industry would also benefit from using robots in the work site to reduce workplace accidents.