They will usually refund you if you end up getting charged because you forgot to cancel. It isn't worth the headache of a chargeback.
Plus they have to pay a fee for chargebacks regardless of whether they think it's valid or not, so strong disincentive.
It's way easier to just not give them a way they can charge you. That way you don't have to deal with a support representative fakely asking you how your weekend was, and who doesn't actually care about your weekend.
Funny, I got a fraud call recently because CrunchyRoll decided to try to renew a subscription I abandoned years ago and the card they have is expired.
I know it wasn't me because I gave up entirely on the service after they changed something about their login systems to reject my password and I could no longer get in. Support wanted me to jump through a lot of hoops and I just refused, choosing instead to just stop doing business there because I wasn't really watching anything at that point anyway.
This was around 2022, mind you, so they tried to renew me after several years with no explanation.