A host may have a requirement that Government Identification is on file with Airbnb for instant bookings, but bookings will still go through without the ID on record. The only explanation I have had from Airbnb is that some hosts are OK with this.
Instant booking does seem to help in the rankings and get you more bookings, so rather than complain, I send this saved message below to guests without ID on file immediately after getting the booking. I have used it at least half a dozen times, and all guests have uploaded their ID to date.
The lesson I have learned is that most guests want to comply and do the right thing. Also, as a host, using saved messages is an incredible time-saver that helps you be a better host and run a smoother business.
Saved Message
The Airbnb system has, in error, permitted you to instant book without meeting host requirements. Please be sure that you have a government ID on file with Airbnb before your arrival to avoid a last-minute cancellation.
These steps may help you go through the process to take a photo of your Government identification and upload it to Airbnb. The details are confidential and remain private with Airbnb. It does confirm for hosts that your identity is verified, and that makes it easier for hosts to accept your booking request.
If you are working on a computer, it may display this way.
Click on the top right photo. It brings up a dropdown menu.
Click on Account
It should display Account Settings. It displays information in separate boxes. Click on Personal info box>
Scroll down this page to Government ID and follow the instructions to take a photo and upload to Airbnb
If you are using your smartphone, it may display this way.
Click on your Airbnb profile it should be on the lower right, then
Click on personal information
It will show as edit profile.
There will be a Government ID item on this list. Click on Government ID The application will prompt you through the photo process. Let me know if you have any problems.