Because most investors are investing in more than one company. If someone has a stake in Google, Microsoft, and Confluent, and their ROI for the first two are great this quarter, but Confluent is lukewarm or even in the red, they're going to want an explanation.
They can be told that products are great, or employees are producing a lot, but the only thing that matters to investors is the money. And so, when you're underperforming compared to others in your market, you have to do what appeases the shareholders, and that involves culling employees.