Originally Posted by SpaethCo

Disney+ and ESPN+ are available individually as annual subscriptions for a ~20% discount, and if you are already subscribed to those services before signing up for the Disney bundle through Hulu your monthly Hulu bill is reduced by the full monthly price of each of those services in addition to the bundle discount being applied. It's the same deal with services like Audible where you get a pretty substantial discount for annual billing.

Basically the credit being limited to monthly increments encourages you to subscribe to these services in their most expensive form.