Why should you learn how to add when you can just use a calculator? We've had calculators for decades!
Because understanding how addition works is instrumental to understanding more advanced math concepts. And being able to perform simple addition quickly, without a calculator is a huge productivity boost for many tasks.
In the world of education and intellectual development it's not about getting the right answer as quickly as possible. It's about mastering simple things so that you can understand complicated things. And often times mastering a simple thing requires you to manually do things which technology could automate.
Because understanding how addition works is instrumental to understanding more advanced math concepts. And being able to perform simple addition quickly, without a calculator is a huge productivity boost for many tasks.
In the world of education and intellectual development it's not about getting the right answer as quickly as possible. It's about mastering simple things so that you can understand complicated things. And often times mastering a simple thing requires you to manually do things which technology could automate.