Many companies currently require that you call in person - during business hours only - to cancel, wait half an hour (or more) on hold to speak with a person who will get fired if too many customers successfully unsub.

Adobe's call centers have a script where they offer some "bargain" deal if you don't cancel which converts your for-real-monthly-with-no-cancellation-penalty subscription into one that has an annual requirement and a "cancellation fee" that is in effect the rest of the year's subscription charge.