He would rather be that much more powerful in communicating his ideas to a smaller group of people and alienating people like you. By you, I mean someone who thinks "what 19 year old wrote this?" or similar.
He outlined this in the article. He gains a deeper engagement with some people at the expense of losing others.
He isn't concerned about losing you, dear reader.
(ETA: Interesting, HN won't let me reply to a downvoted reply to my post.) Verbose defenders & detractors of the practice aside, methinks many who murmur support do so from social pressures, and in fact dislike the practice but won't or can't articulate their opposition.
That is a really interesting question.
I agreed completely with Zach's post, and I've agreed with all of @gks's comments in this thread. Zach's use of swearing increases my emotional connection to what he's saying. If Zach didn't swear, he would connect less with me.
But the plural of anecdote is not data. What proportion of people are like you, and find swearing in a talk trite and cheap? What proportion of people are comfortable with Zach's slides?
We should do science.