Why is there a cap on ecumenical keys?

Just wondering why there's a cap on ecu keys?

I know there's a reward from wildy diaries to increase the limit but is it op to be able to stack ecu keys if you have wildy elite done?

I feel it would be a nice QOL for doing spiritual creatures tasks but I don't think I know enough about gwd meta/money makers to know if it would be OP or anything like that.