Because she refuses to talk specifics about the technology. And the subtext is that Theranos has been able to attract such a high valuation based on her personality even when the technology isn't apparently there.
The sound of that is almost hilarious so I took a look. There are two pictures of her in the rotating highlights things and one on the company page. I clicked around on at least 10 other pages or so and didn't find any more pictures. Didn't seem like "everywhere" to me unless I happened to visit the few pages without her photo.
There are 3/6 in the rotating thing. She is the first face on Company, actually it's a one minute video of .. just her. Leadership is a jumbotron with a quote of her. Careers has another quote with bonus picture, I love this one:
“The minute you have a backup plan, you've admitted you're not going to succeed.”
Elizabeth Holmes is a category filter on their News page.
What else does a chief-executive have? Number crunching is left to the CFO. Engineering strategy to the CFO. Domain knowledge to the CMO. Operating strategy to the COO.