Why must the fresh leaves, cilantro, typically be reserved for garnishing or added at the very end of cooking processes?

Cilantro's volatile oils dissipate rapidly under heat

The difference between preparing coriander seeds and cilantro leaves lies in the stability of their active chemical components when exposed to thermal energy. While the seeds possess robust compounds that benefit from slow cooking or roasting to release their warm, nutty flavor, the characteristic bright, citrusy flavor of cilantro comes from volatile essential oils. These oils are highly susceptible to heat; they evaporate quickly when exposed to high temperatures or prolonged cooking times. Therefore, to preserve the distinctive zest and aromatic profile that cilantro contributes, it is standard practice to add it only during the final moments of preparation or use it raw as a garnish.