Those two don't go to meetings where they need to leave an impression on someone.
When the CEO of my company (who wears jeans day to day) goes to a meeting with a new client, we wears a suit and tie so that the first five second impression the client gets is 'he isn't taking this seriously'.
That's why this way of thinking is very much not outdated - its a quick and effective way to show commitment to something, even if in meetings going forward people are much more casual..
So when you see Zuck speaking to an audience, is your thought more likely to be "Wow, this man is powerful, we need to take him seriously!" or is it, "Aw shucks there's Zuck, I can't believe he made a billion dollars"?
It depends on the person. I am still in college and if you go to the business school, the students in there will say that a suit represents power. If you go to the CIS building it is the opposite. I have seen it, even though I do not think that a suit represents power, a lot of people still do.
