[asoneth]

To be fair, it's not just investor greed that does it.

Plenty of good managers and engineers just want more money too. Once the hyper-growth stalls, many early employees cash out their lottery ticket and leave to take higher-paying jobs elsewhere. They don't care as much about maintaining the product and experience that they built as they do about making more money.

(And this is exacerbated by the fact that many people prefer building new things than to maintain the existing things they built.)