Stripe's old approach was quite direct: the CC companies charge us (and don't refund) for refunded payments and chargebacks, so we pass those on to you.

Quite reasonable, but the new policy is taking advantage of the fact that they have the rare ability to fix this broken interface instead of just passing it on.

Refunded fees for refunds encourage easy refunds to dissatisfied customers. Offering refunds without crazy hoops to jump through is generally just good customer service (especially for service-related businesses where you don't have to worry about lost inventory!) -- it can quickly put a problem into a realistic context (and customers can realize "well, it's not perfect... but it's actually still worth keeping"), which makes them less frustrated.

I offer a refund first to a lot of tech support questions (i.e., "this isn't working on my computer"), and hardly anyone actually wants one, but it comforts them. Knowing that my fees would be lost make it less pleasant for me to offer... this is psychological pain (the actual cost is minimal), but I always appreciated PayPal's policy for this reason.