Wall Street is back. Encouraging as the banks’ first-quarter figures were, however, they do not mean that the need for hard strategic thinking has vanished.

The rebound in trading revenues should not tempt banks that have decided to retreat from the arena to reconsider that choice. The giants of fixed income, currency and commodities that profited so handsomely in the quarter from their constancy to trading, still face long-term performance issues in the post-crisis market-making business.