>Licenses like the MIT and BSD license exist for a different reason. And that reason is to give people who want to share what they did on generous terms a way to do so. And historically this was done in the belief that enlightened users would see it as being in their interest to contribute back.

And this works on an individual level, but once corporate bureaucracy gets involved it tends to turn into "why would we give away proprietary code?". GPL has its flaws, but it helps to fight short-sightedness.