It's pretty easy to understand why keywords are highlighted, even if it isn't justifiable. 1) Programmers are lazy, 2) regexes are the quickest way to implement basic syntax highlighting, and 3) if your keywords are reserved words (as most are), then you can get infallible highlighting with the expression /(^|\s):listofreservedwords:(/s|$)/.
Emacs, at least, already provides primitive parsing / heuristics that work reasonably well for most languages. See the example in the link I posted above: All I had to do was customise the colour and font-weight of various things already recognised by Emacs: function-name, variable-name, type, etc.
Maybe what I don't understand is all the effort people put into making pretty themes for their editors --there are millions of these themes out there-- and almost all of them insist on highlighting (drawing attention to) the language's keywords of all things. The least important part of any program.
