Render cracks suck in water. When it is raining, it is common to see da dribble of rainwater running down a rendered wall until it meets a crack, then being drawn in, disappearing within to cause ingress. Sometime only the external wall is affected, causing heat loss inreasing the risk of condensation. Sometimes the water causes penetrating damp and occasionally timbers become damp, risking rot.
Dampness in bricks reduces insultion by a factor of about 50%, so even if the rain doesn’t actually penetrating through the wall, the increased susepticibility of one a section of wall to become damp, reduces internal temperature increasing the risk of condensation and mould. A good example is where the uppeer section of wall is painted or render, and the lower section exposed, resulting increased dampness on the external skin causing bricks to lose heat..
In London cement-based plinths about half a metre high, are commonly used to reduce dampness caused by rainwater splashing onto wall.