Here's why:

* Solubility Rules: General solubility rules indicate that hydroxides of heavy metals are typically *insoluble* in water.

* Equilibrium: While a tiny amount of lead hydroxide will dissolve, the solution reaches an equilibrium where most of the lead hydroxide remains as a solid.

* pH Dependence: The solubility of lead hydroxide is pH-dependent. It is more soluble in acidic solutions due to the reaction with H+ ions to form soluble lead ions (Pb²⁺).

In summary: While technically not completely insoluble, lead hydroxide is considered practically insoluble for most purposes.