If you write code that other people have to ask you about, you will reach a point where you don’t have time to write code anymore because you’re too busy answering for your own code. You may interpret this as “helping your less fortunate teammates” but the wise know they can reduce your influence on the team by sending more people to ask you questions.

Giving them more time to clean up your mess and you none to make it worse.

Sites like Codewars seem to me like good ideas starting out, but it doesn't take that long to turn into an arms race of complex one liners that people vote up as the coolest solution, not the best in terms of productivity for a company.