Jane Galt wants to buy a car.  So she looks at a website, and doesn’t find the one piece of information she most wanted – and indeed concludes that that information is not there to be found:

This is what happens when the commercial team runs roughshod over
editorial. The general rule about a website is that people have three
or four things they might want to do when they go there. The rule of
good design is to make those three or four things very prominent on an
otherwise simple page, and let them go to it.

Commercial does not like that. Commercial wants to sell ads. And
tie-ins. And sponsored links. They also tend to believe that if you
don’t throw every single possible link in front of the user all at
once, the stupid readers won’t view your pages. And if they have too
much pull, you get a web page that drives readers away in disgust. The
first rule of commercialising the web is, you can’t sell stuff to
people who just hit the "back" button.

Don’t get me wrong: if commercial has too little pull, you get a web
page that loses money and has to be shut down so they can afford to
fire everyone. This is where a good UI guy is worth his weight in gold.

We don’t have the pressure from ‘commercial’ in that same way, of course.  But for very different reasons, it can be hard for us to concentrate on what really matters to customers who want to get something done.