The Files app was first introduced on the iPhone with the release of iOS 11. In the two years since they were introduced, we have gained a desktop class experience, as there is finally a decent file manager for mobile devices. That said, there was always a big problem with the file app, a problem that finally fixes iOS 13.
Files work just as well as any other file management system. You can create folders, put documents in these folders, and move and sort your content as needed. Before iOS 13, however, you could not create new folders with the appropriate name "On my iPhone". This meant that all new folders were reserved for iCloud or third-party storage services ̵
That was all in the past now. To create a new folder in "On my iPhone", just long-press on an empty space and then tap "New Folder" in the context menu that appears. Alternatively, you can swipe down the screen to display the omission symbol (•••). Tap on it and then click on "New Folder" in the action sheet. When prompted, enter a name for the folder. Tap "Done" and you've already created a locally saved folder directly on your iPhone.
It's time for Apple to add this feature to Files. While ICloud is not necessarily insecure, does not provide the same level of security as local storage (assuming you have a strong enough passcode). You can create and save folders anywhere in files, locally or cloud-based. Now it's up to you.