Why is high boiling substance often distilled at high reduced pressure?

High boiling substances are often distilled at high reduced pressure to lower their boiling points, which minimizes thermal degradation and preserves the integrity of the compounds. Distillation under reduced pressure allows for the separation of components without subjecting them to high temperatures, making the process more efficient and safer. This technique is especially useful for heat-sensitive materials, as it prevents decomposition and maintains desired chemical properties.