Customers whose events are cancelling are getting travel credits, often without change fees, from major airlines. While hotels are waiving cancellation penalties and refunding non-refundable bookings, airlines are not.
For a leisure traveler perhaps they’ll use a travel credit for another trip in the future. In most cases they’ve got 12 months from original date of purchase (not date of the trip) to use the credit. For managed business travelers their company may be paying for the booking directly, and is on the hook for trips not taken. But what about unmanaged business travelers who submit receipts for reimbursement after a trip?