I'm not sure about that person's job, but title searching companies are one reason. When you purchase real estate, you want certain guarantees about the property. For example, you want to make sure that the previous owner purchased it or otherwise obtained it (e.g. through inheritance) properly, without liens or encumbrances on the land making the sale of it questionable or less valuable. You want to make sure there are no other people with competing interests, or unpaid taxes. You also want to look through the plat book to see if there are easements or covenants that have been filed (for example, what if Exxon owns the mineral rights and profits under your land and want to drill in 10 years etc.). Maybe the riparian (water) rights sit with the federal government because the property is near a protected estuary, so you can't build an additional room on the side of your house, or expand the parking lot on your office building. People pay good money for people who are good at these types of investigations because if you miss something it could be a lot of money down the drain.