> There's a serious chicken and egg problem here. Adding proper markup
> to documents is a painful and expensive process for little to no
> benefit. That's a hard sell to bosses and overworked designers. So

It's difficult if you start by designing for appearence.

> Browser and authoring tool vendors need to invest time and energy in

Vendors are businesses, which means that they do what is good
for the shareholders, not what is good for the world.  Giving
authors what they want, rather than what they ought to want, 
is usually more profitable.