There are several possible reasons. He could fear for his safety. He may want to avoid the media frenzy. He may assume, rightly so, that many people would dig into his background in a character assassination attempt to delegitimize Bitcoin. And I think at this point Satoshi might realize that Bitcoin is better off without a leader. If his vision was a completely decentralized and egalitarian currency, I think the lack of a founding father helps with that.

Of course, Satoshi may not be just a single person. If Satoshi is a group of people, I would think that there is some sort of contractual obligation that prevents the members from revealing any information.

Adoption of new tech in our daily lives is slow and tends to come later. Adoption by business is comparatively lightning fast and FOMO is strong and justified because it’s a dead serious threat to a company’s existence (Ex: Kodak, Blockbuster.)
So yeah, I totally believe mass adoption by business and institutional investors is imminent.

 For regular Bitcoin users, donating money in bitcoin is incredibly easy. Much easier than donating using a CC or Paypal.
 Plus, many Bitcoin users are enthusiast enough about the cryptocurrency that the fact that a charity accepts Bitcoin will be an incentive to donate in itself. By donating bitcoin to a charity, you are both supporting the charity and supporting Bitcoin, and that's something many Bitcoin users are keen on.