I maybe off the mark here, but since the b2 days there was always a plain template to use. In wp’s case it’s called wp.php. I usually design the site then include the wp.php. It works quite well and I can design whatever I want using css and html.
I think that if they are plain, it’s just reflecting skill, design, and or imagination. Also it’s a matter of taste.
Just saying. I’ll continue lurking now
