Why do subscriptions on Tuned require a credit card?

The TLDR is we disable it to protect our users.

You may have wondered at some point why Tuned hasn't enabled withdrawals from its users' exchange accounts to pay subscription fees. The problem for us is that transactions in the crypto world are irreversible. Allowing widespread automatic withdrawals is too significant of an attack vector. One breach could potentially drain millions in AUM. We acknowledge that withdrawing from user accounts would solve a lot of payment drawbacks, but to us it simply isn't worth the risk.

For this reason we stress in our API guides that users disable withdrawals. If you enabled this when connecting to Tuned please change your settings now.