This right here. This is actually very important. Disney had ZERO obligation to give people on that cruise ANYTHING. Officially they have met their contractual obligations. Regardless of it was weather, mechanical, or any other reason. Now is it a bummer? Yes, I'm not saying it isn't.
At $100 a cabin, I recall around 1200+ cabins on the Wish,
DCL spent over $12,000 giving OBC when they didn't have to. They gave 1200+ 20% future cruise discounts, which lets just say averages to roughly $2,000 in discount (yes some will be less others will be more but just for example purposes). So DCL essentially shelled out $2,412,000 in OBC and future discounts WHEN THEY DIDN'T HAVE TO DO ANYTHING on something that was likely out of their control. I doubt anyone ever expected a mechanical issue of this magnitude on the newest ship.
Now will everyone use the 20%, no most likely not, some people are 1 and done cruisers. The offer was still made to help compensate guests for their inconvenience but we need to remember their contractual obligation was already met so they didn't have to do anything.