No. You can have your locksmith “re-key” your locks. Re-keying a lock is the process of replacing the tumblers (pins, wafer tumblers) of a lock cylinder with new tumblers of different sizes. A new key will coincide with the new tumblers, and the old key will no longer work. In other words, it is not necessary to buy new locks.
Re-keying locks is something that should be done if you have moved into a new residence or lost a set of keys. Most automobile locks can be Re-keyed as well. Re-keying locks is usually significantly less expensive than replacing locks.