Punctuation, especially the use of commas, is not well understood by most people.
That's about all there is to it.

I don't know what the percentage is of people in the United States, for example, who are even capable of producing true publication-quality prose without assistance of a trained copy editor, but I'll bet that figure is less than one half of one percent -- and probably not even half that.

I think we have also discussed elsewhere the drift in language education away from the strict enforcement of typographical formalities and towards 'whole language,' 'functional grammar,' and argumentation. There must be over two dozen different words for the basic concept. Personally, I am all for it, because I think the evidence is clear that we are actually producing better communicators over all.

But if one does embrace that decision, one also has to accept the consequence of an increased number of people who do not get trained or groomed in the habits of copy editing for conformance to standardized speech. It's just the simple fact that we now have a lot of otherwise very highly educated and articulate people that write a lot, but who have also grown comfortable with outsourcing the finer details of grammar and punctuation to computer programs and when computerized support is not available or inadequate, simply not worrying too much about it.