Why is it important to evaluate causes and effects in history?

It is important because if the cause didn't happen the effect wouldn't exist

History is recorded primarily so we (humanity) can keep track of our past mistakes and what happened as a result of something. We teach history so that people can learn from it and not repeat the bad parts, and repeat the good parts. So it's important to evaluate if the cause had a good or bad effect, so you know if you should try something again, or if you should avoid doing something.