It needs far more features apparently. Tons more. That's why Notepad++ is popular. Which also had a severe security vulnerability recently. Which was actively exploited by some state actor like China.
The OS provided option can be bare bones, stable, secure and just utilitarian. This promotes having people choose their own tools for the features they want and not really expecting much other than reliability from the OS version. They didn’t need to mess with a good thing.
Ok, tabs, I do like the tabs.
That recent Notepad++ incident was a supply chain attack, not a vulnerability in the original program.