Here's why:

* Covalent bonds are strong: Covalent bonds involve the sharing of electrons between atoms. These shared electrons create a strong attraction between the atoms, holding them together.

* Water is a polar solvent: Water molecules have a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows water to interact with ionic compounds and polar molecules, but it does not typically have enough strength to break covalent bonds.

However, there are exceptions to this rule:

* Weak covalent bonds: Some covalent bonds, particularly those with low electronegativity differences between the atoms, can be broken by water. For example, the bonds in some carboxylic acids can partially dissociate in water, leading to the release of H+ ions and the formation of carboxylate ions.

* Hydrolysis: Certain covalent bonds can be broken by water through a process called hydrolysis. This involves the addition of a water molecule to the bond, breaking it and forming two new molecules. For example, the hydrolysis of sucrose (table sugar) breaks it down into glucose and fructose.

* Acid-base reactions: Strong acids like hydrochloric acid (HCl) can donate protons (H+) to water, breaking the covalent bond in the HCl molecule. This leads to the formation of hydronium ions (H3O+) and chloride ions (Cl-), effectively dissociating the HCl molecule in water.

In summary:

Covalent bonds are generally very strong and do not readily dissociate in water. However, there are exceptions involving weak covalent bonds, hydrolysis reactions, and strong acid-base reactions.