I was reading about dependency grammars on Wikipedia, and then, following up on the term "(non-)projectivity", was lead to the page about discontinuity. Now, the concept is quite easy to understand, but what I don't get is how
[a]ll theories must have a means of addressing discontinuities.
Now, I am a native German speaker (and not a linguist by training), so all kinds of scrambling words and phrases, with non-projective (naive?) parses, seem to me like a perfectly natural thing (if a language allows them). But it appears that there is a thrive for syntactic theories to avoid ascribing ascribing discontinuous parses (e.g., here is a whole section dedicated to how projectivity might be "violated", and this problem be "addressed"). I don't really get why this should be.
- One reason I can think of is purely practical: some (automata-based?) parsers might have a harder time with non-projective structures.
- Also, in a certain sense, continuous structures are more "aesthetic": the hierarchical and the linear sentence align.
But these are both quite extra-scientific rationalizations. I do not see a reason why a theory should not freely make use of non-projective structures to describe languages -- avoiding them is a purely topological constraint, as opposed to, say, requirements involving heads and government, for which there exist (IMHO) quite natural linguistic explanations.
So, what am I missing? Am I just misinterpreting things and "addressing discontinities" is not a major thing at all?