Not all infectious agents and their toxins are instantly killed by boiling. For example, the hepatitis B virus is destroyed after an hour of boiling.
The second disadvantage of boiling, all non-volatile toxic substances are preserved: nitrates, pesticides, radionuclides, heavy metal salts, pharmaceuticals, including antibiotics, which may be contained in tap water.
Third. When boiled, chlorine interacts with various organic substances and forms carcinogens.