The dispute is a he-said/she-said. Whichever side wins, the underlying problem is the same, and it sits with the merchant.
Visa 13.2 (cancelled recurring transaction) is filed when the cardholder says they cancelled a subscription and were charged anyway, or says they never knowingly signed up for the recurring billing in the first place. The dispute is a he-said/she-said: the cardholder swears they cancelled; the merchant's records say they did not. The case turns on which side has documentation of the cancellation attempt.
Most merchants do not have documentation of what they did not record. A customer who tries to cancel by emailing customer service, by calling a phone number that goes to voicemail, or by clicking around a settings page until they give up has cancelled in their own view, even if no event was logged in the merchant's billing system. From the merchant's side, nothing was processed, and the recurring charge runs as scheduled until the chargeback is filed weeks later.
Merchants who instrument the cancellation flow stop seeing 13.2 at any meaningful volume. The instrumentation is small: a cancellation page reachable in one click from account settings, a confirmation event written to the billing system at the moment the customer confirms, an email receipt within minutes of cancellation, and a screenshot of what the page showed on the day of the action stored against the customer record. With those four artifacts on file, almost any 13.2 case is winnable; without them, the same case is mostly not.