I think the general idea is that if they make it difficult enough, some people might just decide that it's not worth canceling. I'm sure there's some metric that says most people canceling a subscription are unlikely to resubscribe, so making it difficult to do so probably increases the likelihood of keeping you by some small percentage, offsetting your likelihood of coming back.

The NY Times is a great and slimy example of this. Canceling the subscription requires a phone call or online chatbot, which make a people less likely to cancel. When you do try to cancel, they offer you a deal to stay. You have to reject that deal to finally cancel your subscription. While this is clearly a bad customer experience, I can almost guarantee that it increases their retention rates.

Ultimately, a business is hurt a lot less by giving a poor experience to someone already canceling their subscription.