I want to relate the experience I had with American Airlines yesterday, I did not see this documented, but it may be a nice bonus if you can get it.
While checking on our trip, I discovered that AA had just made a major change on our late August trip (why their computer did not notify me by email I have no clue), in that they have now cancelled the direct return home from Dublin to Philadelphia, and gave us a terrible rerouting. Needless to say this would not work, aside from the fact that this trip will almost surely not be allowed to fly anyway). Since they could not give an improved routing without raising the cost, we decided to cancel the trip and accept the refund. And this is where I found it interesting.
After stating on the refund screen that we wanted the refund and not a voucher, we were then presented with a pop-up that offered us 20% more for taking the vouchers. As the voucher itself would be good for use for one full year -that is for cashing in the voucher, not the actual trip date - and we are trying to reschedule this entire trip anyway, this looks like a winner. Current AA policy is new trips booked my May 31 can changed without a change fee, and a ticket expiring before Sept 30 can have its value kept for travel through the end of 2021. I made an additional call to clarify, and indeed if we used the voucher and then that trip scrubbed then we would be refunded with a new voucher, still good for a year (although this will not get another 20%). So as soon as the voucher hits later this week, will just re-book this trip for an acceptable return flight.
Bottom line -although not directly promoting this, it looks like American is giving a 20% increase via voucher in order to keep you as a passenger and not have to lay out their limited cash. YMMV.