Why, if covalent bonds are stronger than ionic, do they have a lower melting point?

The atoms of covalent materials are bound tightly to each other in stable molecules, but those molecules are generally not very strongly attracted to other molecules in the material. On the other hand, the atoms (ions) in ionic materials show strong attractions (electrostatic force of attraction) to other ions in their vicinity. This generally leads to low melting points for covalent solids, and high melting points for ionic solids........