These scavenger hunts aren't merit based reserved tickets. What do they actually do? Who are the targets, and why does Google want these people to attend I/O?

The answer can't be "developers" or "to learn things." Not while the prevailing reason people attend I/O is to get the new shiny toys and the primary means for getting a ticket is a random lottery with no prerequisites for entry and no fee to prevent gaming. What we need for learning is mostly put on YouTube promptly, so presence is not necessary there, either.

I don't understand it at all.