Kinetic Control
A lot of reactions that are thermodynamically favorable don’t actually occur in real life. For example, the reaction of diamond turning into graphite is thermodynamically favorable at room temperature. However, these reactions happen very slowly and aren’t visible due to kinetic control.
If we recall the Maxwell-Boltzmann distribution, only particles with high enough energies will be able to react to form the products, meaning that for certain reactions, the percentage of particles with that required activation energy will be small enough to be considered negligible.