I and many authors live in countries where PayPal (or its alternatives) is not available. For this reason, we can neither receive money through the reward program, nor ask for donations using services like PayPal. The amazon coupons are not for these countries either.
Currently the most promising borderless method of money transfer is Bitcoin, and maybe a few other major crpyto-currencies. Adding support for Bitcoin would let the authors access their well-earned rewards, create a healthy environment for those who maybe need it the most, and open the gates of mod authorship to a huge share of people in the world who are currently discouraged to start due to the lack of access to rewards.
With regards to Bitcoin, use of a technology such as the Lightning Network can allow the payment cost to be virtually zero, with instant settlement.