Explain why nucleophilic substitution reactions are not very common in phenol.

In phenol,the oxygen atom of the $-OH$ group is directly attached to an $sp^{2}$ hybridized carbon atom of the benzene ring.
Due to resonance,the $C-O$ bond acquires a partial double bond character.
This makes the $C-O$ bond shorter and stronger compared to the $C-O$ bond in alcohols,making it difficult to break.
Furthermore,the benzene ring is electron-rich,which causes repulsion between the incoming nucleophile and the electron-rich ring,thus hindering nucleophilic substitution reactions.