Imagine doing something out of passion and goodwill.
If you work an honest 8h, there isn't much bandwidth left. Also, money.
According to linkedin and Google high ups, you need to do an honest 60-80h a week as an employee so you can gain the highly lucrative, liquid and bullish asset of your boss maybe remembering you worked 60-80h a week.
Yeah, and how good it feels when random people come complaining about you not adding a feature they want for free or not being responsive enough! /s