In a world where XML with DOM and SAX exist, there is no difference. Now imagine that all this and all related technologies (and there are quite a few...) would

In a world where XML with DOM and SAX exist, there is no difference. Now imagine that all this and all related technologies (and there are quite a few...) wouldn't even have had to be invented :) ...because you could have just used one parser, that you developed for the language in the first place. Think of the amount of code duplication in all the parsers for all the languages and file formats! I argue that the point should always be to reduce complexity of the systems and keep them DRY, even at the cost of slightly less functionality and slightly worse performance. Mainly because the introduction of complexity in a system tends to be irreversible in practice (whereas performance can always be better tuned and more functions can be added when/if needed). Now, in the real world, where the complexity of XML and friends (and this is probably not even the best example) has already been introduced, and where you can't make it disappear because you have so many things that depend on it now, you're right, there is no real benefit of the fact that you can also do it in a simpler way. And most pro-Lisp arguments hit the same walls: yes, you have a more elegant way to do things, but the complexity of the other ways of doing the same thing has already been introduced and it's not going away, so there's usually little benefit for also having simpler ways to do things.