What are good uses for class helpers?

Delphi (and probably a lot of other languages) has class helpers. These provide a way to add extra methods to an existing class. Without making a subclass.

So, what are good uses for class helpers?

What can classroom be used for?

You can use Classroom in your school to streamline assignments, boost collaboration, and foster communication. Classroom is available on the web or by mobile app. You can use Classroom with many tools that you already use, such as Gmail, Google Docs, and Google Calendar.

I'm using them:

To insert enumerators into VCL classes that don't implement them.
To enhance VCL classes.

To add methods to the TStrings class so I can use the same methods in my derived lists and in TStringList.

TGpStringListHelper = class helper for TStringList public   function  Last: string;   function  Contains(const s: string): boolean;   function  FetchObject(const s: string): TObject;   procedure Sort;   procedure Remove(const s: string); end; { TGpStringListHelper }