Not everybody is writing web apps.

You can also see it differently: If the language dictates a 4x increase in memory or CPU usage, you have set a much closer deadline before you need to upgrade the machine or rearchitect your code to become a distributed system by a factor 4 as well.

Previously, delivering a system (likely in C++) that consumed factor 4 fewer resources was an effort that cost developer time at a much higher factor, especially if you had uptime requirements. With Rust and similar low-overhead languages, the ratio changes drastically. It is much cheaper to deliver high-performance solutions that scale to the full capabilities of the hardware.