No, they are not required by law.
However, if the property is mortgaged, the lender will want title insurance. Almost all title insurers will ask for a survey to verify that the property and any structures are free from encumbrance or encroachments. The title company will pass the cost of a survey on to the mortgager. Be sure that you are not being charged the price of a new survey if an old one is being "passed" forward. In either case, be sure to get the survey certified in your name and keep a copy of the survey plat for future reference.