In addition to the simple "Pay with PayPal" button scenario where you get all the simple subscriptions-as-a-service features built in (automatically handling failed payments and retries and notifying you of subscriptions, payments, cancellations, expiration of services, etc)... they'll also power your normal credit card payment forms on-site, and do token-based recurring billing (authorize payment once, charge the customer a variable amount whenever you need).
That startups discount PayPal entirely because it's "not cool" and you can't chat with the founder at 4AM about your implementation is astounding to me. All of these other services are very expensive, less fully featured, and none of them come with 240 million pre-registered users and brand trust. Any reasonable decision maker should be at least considering them an option.