Benzene has a resonance energy of ~150 kJ/mol. In EAS, the sigma complex temporarily loses aromaticity, but the final product REGAINS it (net: only lost and regained during TS).

In hypothetical addition:

• Product would be a cyclohexadiene derivative — permanently lost aromaticity
• This is thermodynamically ~150 kJ/mol less favorable than substitution

Evidence: Benzene does NOT decolorize Br2/CCl4 (no addition in the dark). It requires a Lewis acid catalyst (FeBr3) to undergo substitution. Compare: cyclohexene rapidly decolorizes Br2 via addition.

Exception: Under extreme conditions $\frac{high T}{P with special catalysts}$, benzene can undergo addition: H2/Ni at high T and P → cyclohexane. Cl2 under UV → hexachlorocyclohexane (BHC — Gammexane).