If BTC doubles, your allocation shifts. Rebalancing forces you to take profits on winners and buy laggards systematically.
Use a 5% drift corridor. Only trade if an asset drifts >5% from target to minimize fees and taxes.
HODLing winners too long increases risk concentration. Rebalancing resets your risk profile to your baseline.
Use Layer 2s for frequent rebalancing to avoid gas drag eating your alpha.