Why do people buy a bunch of individual stocks that are in the S&P instead of just buying the index fund?

I usually just DCA in the S&P 500, but the times I bought Amazon, Google etc individually I didn’t outperform the S&P, the only time that happened was just sheer luck with stocks like NIO before it exploded (and got lucky when I sold at the top). Why do I see a lot of posts with people heavy into a bunch of tech stocks that are listed in the index funds anyway? Just curious !