Ask HN: Why would anyone share trading algorithms and compare by performance?

I was speaking with a person years my senior awhile back, and sharing information about the Quantopian platform (which allows users to backtest and share trading algorithms); and he asked me "why would anyone share their trading algorithms [if they're making any money]?"

I tried "to help each other improve their performance". Is there a better way to explain to someone who spends their time reading forums with no objective performance comparisons over historical data why people would help each other improve their algorithmic trading algorithms?