Managed paths allow a SharePoint administrator to define new URLs to better represent site collections associated with a Web application. By default, each Web application includes three managed paths: (root), sites, and my.
The my path is only included if you use the configuration wizard, which creates the People service application and MySite Host automatically. If you create Web applications manually only the (root) and sites managed paths are included by default. The sites path is reserved for site collections, and the my path is reserved for MySites.
Imagine if several SharePoint site collections, in addition to the root site collection, have been introduced as part of a new SharePoint deployment that includes IT, HR, ...