Why do you need to buy title insurance again even though you purchased a policy when you first bought your home and there is no change in ownership?

It's because a separate policy is needed by the lender insuring the validity of your mortgage when it is made.

For as long as you own the property your mortgage is valid, but it doesn't insure the new mortgage created when you refinance, and it doesn't provide protection against events that may have transpired between the time you purchase the property and when it is refinanced.

For example, you may have taken out a second mortgage on the home that could threaten the priority of the new lender's mortgage. Or, there could be legal judgements against you or a mechanic's lien against the property by a supplier who wasn't paid for home improvements.

Lenders also insist on a new title policy because many mortgages are packaged as securities and sold to investors in the secondary mortgage market. Title insurance is the only practical way to provide the assurance investors demand and to ensure that the mortgages backing these securities are valid and enforceable.