A recovery seed (or seed phrase) is the ultimate backup for accessing your cryptocurrency wallet. Failing to write it down securely poses serious risks:

1. Permanent Loss of Funds
If your device is lost, stolen, or damaged, your recovery seed is the only way to restore access to your crypto. Without it, your assets are irretrievable no customer support can help recover them.

2. Vulnerability to Device Failure
Hardware wallets like Ledger or Trezor can malfunction. If you haven’t recorded your seed phrase, you lose all access to your funds stored on that device.

3. No Recovery After Theft or Loss
If your phone or computer with a software wallet (e.g., MetaMask) is stolen or crashes, the seed phrase is the only way to regain control of your wallet. Without it, your crypto is gone forever.

4. Risk of Human Error
Forgetting passwords or PINs is common. A recovery seed acts as a failsafe; without it, even a simple mistake can lock you out permanently.

5. Inability to Migrate Wallets
If you want to switch wallets or upgrade devices, you need the seed phrase to transfer your funds securely.

Conclusion
Not writing down your recovery seed is like throwing away the only key to a safe. Since blockchain transactions are irreversible, losing your seed means losing your crypto forever, with no recourse. Always store it securely offline.