Why does spontaneous reaction occur very slowly and not instantly?

Spontaneous reactions occur slowly due to kinetic barriers such as high activation energy, which must be overcome for reactants to transform into products. While the thermodynamic driving force may favor the reaction, the rate at which it proceeds is influenced by factors like molecular collisions and the need for specific orientations. Additionally, some reactions require intermediates or specific conditions that can further delay the process. Therefore, even thermodynamically favorable reactions can be sluggish without an appropriate catalyst or environmental conditions.