HP printers are designed to work on a wide range of paper types and in a range of environmental conditions (temperature and humidity). HP tries to make printers that will work well for all supported media types. HP also understands that under certain circumstances, some standard product settings might not give the best results. Paper curl gets worse with high humiditiy and high temperature. Low curl modes reduce fusing temperature to try to make the printed sheets flatter. In normal office conditions (relative humidity from 20 to 60%) most paper doesn't curl. If you printed in low curl mode, the lower fuser temperature would produce poorly fused output - resulting in text that might flake or peel off the paper, or pages that might stick together over time.
HP recommends using standard print modes and settings. Only use special print modes, like low curl mode, if you have a problem with curled paper. Also, be sure to set the correct paper type (plan, glossy, cardstock, etc.) in your print driver for best results. Good question, thanks for asking.
Best regards,
Alan_R