The problem is one of context. When editing a programming language buffer, the editor needs to be aware of the entire buffer, because a { on the first line could match to a } on the 1235987th line and affect hilighting as well as editing commands like indentation, or sexp navigation. Meanwhile, ideally, in a log buffer the only information needed to nicely render a single line is contained on that line. Or perhaps the log unit is multiline, but still somehow boundable. In that case the editor should be able to do presentation in constant time based on the segment of the buffer that's visible.

Unfortunately, what with logging in JSON and so on, these two cases aren't really distinct anymore. But if I did want to use one editor for both log viewing and coding, I'd pick the one that was the most easily and interactively customizable.