The graduation speech format is so insanely successful at pulling wonderful, even life changing, thoughts out of fascinating people. But it's also a really inefficient vehicle. Graduation speeches only happen once a year. They only happen at a small number of institutions. And the speakers are chosen in a pretty ad hoc way.
The upside, of course, is that graduation speeches feel important enough to the speakers that they really work hard on them. And there's an implicit cultural agreement around graduation speeches that says we won't judge people pompous for standing at a podium and telling us how to live. If that tacit agreement wasn't there the graduation speech format would be too dangerous for anyone to try.
Still, there must be some format or space that could create a more routine outlet for beautiful thoughts from interesting people about how to live better.