Both solutions provide access to permission defined folders using protocols such as HTTPS, FTP and SFTP. Both have audit trails and the ability to send one-time links, for guest users to be able to download particular files. With so much overlap, what is the difference?
Generally the larger our systems get, the more of an administrative burden they become. More user accounts need creating for access; permissions and controls need to be set correctly for security purposes; and something or someone needs to keep a track of the changes taking place.
When it comes to old technology lurking around in your network, there is as good a chance as any other that an FTP or SFTP server is part, having been a staple of most IT teams for a very long time.