Why should water be never added dropwise to concentrated sulphuric acid?

It is always advised to add acid to water than water to acid. This is because the reaction between acid and water is highly exothermic and so produces lot of heat. Hence, when water is added to acid, it results in vigorous boiling of the solution and the amount of heat produced is so large that it splashes the acid out of the container, which can result in acid burns. On the other hand, when we add acid to water, it is like adding a concentrated solution to water in small amounts. So comparatively lesser amount of heat is released.