Lattice energy and crystal habit answer different questions. Lattice energy measures how stable the final bulk crystal is, and it is dominated by the strong bonds — covalent, ionic, and metallic. Habit is set by growth kinetics: which faces grow fastest during crystallisation, and that is controlled by the weak, short-range interactions at the surface. This is why a crystal can be held together overwhelmingly by strong bonds while its outward shape is decided by forces that contribute almost nothing to its stability.
How Chemical Bonds Drive Crystallisation and Crystal Growth