A truly liberal (in the John Stuart Mill / Enlightenment sense of the word) education gives you the tools you need to engage with the world. How can you ever change society if you are only able to see the world in what makes money, and are never given the time and resources to think beyond what is today towards what could be?
It is true that some people can learn some of these things on their own, but having 4 years to think surrounded by an environment where everyone else is focused on that same goal can really make a difference.
If a pragmatic man like Bloomberg believes in the value of a liberal education (again the old sense of the word), you can bet it's not total hooey.
(although see my other comment for what I believe is behind at least the timing of this announcement)