Notepad++ originated at a time when there weren't many code editors for most of the new, growing languages (perl, python, js), or for editing xml and json, especially on windows. Many of the "good" code editors were expensive and enterprisey, or they were limited to linux, or they had an extremely steep learning curve (vim, emacs). Notepad++ worked on everything, was free, installed quickly, and it was fast. I've used it to replace hardcoded values in binary files before. I think most of the people who are praising it are remembering how valuable it was 20 years ago. I don't know anyone that still uses Notepad++.
I have it on a few thousand servers in my department, mostly as a Notepad that can do more, like comment color or editing small config files of all sorts. It is far from the days I used to write entire small apps in Notepad ++, but we still use it and there is no plan to replace it unless they do something that puts us in danger (ex: stop fixing bugs/security issues).
It's been the "standard" editor at my place of employment, but no one objects to other editors or IDEs being used instead. Our workstations are all Windows, so it's a decent default to install for everyone.
