The attraction is having one editor on all the platforms which developers use (this is one of the few market niches where the users are seriously split between

The attraction is having one editor on all the platforms which developers use (this is one of the few market niches where the users are seriously split between Windows, Mac and Linux). That means it can always be installed no matter what platform you're on, and justifies more effort than would be possible on any one platform, which may cover only a third or a quarter of the market. Also, I wouldn't say there's a clear distinction between an IDE and an editor. People want a modular program, which starts simple, and can be upgraded when the upgrade becomes useful or necessary.