Why does intraday data (1-min bars) not improve prediction accuracy over daily data for the same features?

Question

MLQuiz · Accepted Answer

Tested: 1-min SPY (49K bars) = 50% accuracy, 5-min (11K) = 50%, 15-min (4K) = 50%. Same as daily NIFTY (2.5K bars). More granular data = more noise, same signal. Microstructure features (order book) needed for intraday edge.