Notepad is heavily used as an IDE (Integrated Development Environment) by a lot of people. It’s not exactly a good development environment but it is nonetheless. I would actually argue Notepad is used primarily by programmers, and that casual Windows Notepad users are in the extreme minority. The whole reason it’s so heavily used is because unlike WordPad or Word, it doesn’t include formatting data, which can fuck up computer code.
Notepad++ for example is literally built to be more like an actual IDE and supports color-schemes and indentations for numerous computer programming languages.
Microsoft isn’t entirely stupid (just mostly), and in knowing this, they’re pushing to put their programming Copilot where they think it needs to be: Inside IDEs, which to them includes Notepad.