Foundation walls are under pressure, if the pressure becomes to great the foundation wall will buckle. With cement sealant and bracing further buckling can be prevented and water intrusion prevented.

In the case of the home in this picture there was water penetrating the basement but not at the step crack, as you may think. It was in the corner below the downspout. With the addition of a 6ft extension water was moved away from the foundation and water penetration ceased.

Keep the water away from the foundation.