Indeed, the most effective team will be at least minimally cross-disciplined. I think the desire to generate HTML via code is just a case of unfamiliarity. I've been writing code since 1986 and HTML since 1994, and I have to say that there is no advantage to generating via HTML per se (frameworks like Seaside notwithstanding). If you have a decent text editor it can color and edit templating languages just fine.
Developers should write HTML for the same reason that business people should learn to edit HTML--it's the best canonical format for all stakeholders.