It's like asking why ever read a book, with a level of english past the level of a memo asking if you have completed a task. This article also seems to suggest that people don't understand how to preform basic mental arithmetic.

In the states there also seems to be this insane way of thinking that you should learn an algorithm to do things in a particular way, if you can do it one way you should understand it and all the other methods should just fall into place.

This is a pretty good explanation of the problem. https://www.youtube.com/watch?v=5ZED4gITL28