Ok, I should qualify that. It will eat up oil-based coatings such as fingerprints. Magnesium flouride and other optical coating materials are insoluble in methanol. If one uses a plastic lens, methanol may also not be a good idea.
Of course they are solvents, why else would one use them for cleaning? They are meant to dissolve contaminants sticking to the lens. Water is also a solvent (and an extremely potent one at that), but it doesn't work well for non-polar dirt like grease and oil. Methanol dissolves many polar and non-polar contaminants, is easy to obtain with sufficient purity, isn't highly taxed (like ethanol), and dries off quickly.