I consider it an incentive payment for the organizer to have successfully created a Schelling point which gets people who are worth talking to in one place, at one time, in a very talkative mood.
There is a joke that the main attraction of conferences is the "hallway track." As someone who is likely to be a speaker, this joke excessively centers the existence/experience of speakers.
*Of course* 90%+ of the value is talking to 90%+ of the attendees of the conference.
*Of course* 90%+ of the value is talking to 90%+ of the attendees of the conference.
As a speaker you're 20% creating an artifact for the Internet which will help the right sort of people find the conference the next year, 70% providing mood music for the conversations happening at the conference, and 10% doing knowledge transfer.
(That 20% is contingent on the talks somehow being recorded/etc which, well, different people choose to run their businesses differently, but if the Internet doesn't get a copy of work I'm doing publicly I feel like something has gone disastrously wrong.)
