What is a legacy name and why would one want to clear it at the Shengui Guo Bathhouse?

Pet names used to be unique, meaning no two pets on the entire site could share the same name. Not too long ago, they made the change so names were no longer unique, pets can now share names across the site. To signify that a pet had the name before this change, they got the legacy title added. Some people really didn't want to give up the unique name system and this was the compromise. For people that didn't really care about pets having the OG name, they added the option to the bathhouse to clear the title from the pets. Any pets created after this change will not have a legacy name.

thank you for the thorough and easy to understand answer. ♥