And they protect the US Secretary of State, too, but look at how hard Colin Powell made their job:
https://wikileaks.org/clinton-emails/emailid/30324
It's in the PDF attached to that. There's always a weak link somewhere. When you have people like this in power, even the smartest spies can't protect them --
"Now, the real issue had to do with PDAs, as we called them a few years ago before BlackBerry became a noun. And the issue was DS would not allow them into the secure spaces, especially up your way. When I asked why not they gave me all kinds of nonsense about how they gave out signals that could be read by spies, etc. Same reason they tried to keep mobile phones out of the suite. I had numerous meetings with them. We even opened one up for them to try to explain to me why it was more dangerous than say, a remote control for one of the many tvs in the suite. Or something embedded in my shoe heel. They never satisfied me and NSA/CIA wouldn't back off. So, we just went about our business and stopped asking. I had an ancient version of a PDA and used it. In general, the suite was so sealed that it is hard to get signals in or out wirelessly."