Because GP is talking about theoretical vectors of attack in highly secure environments. Whereas you are now discussing why hackers don’t target devices with zero-financial gain.

Also just because syscall A might be vulnerable to a particular type of attack, it doesn’t mean that service B uses that syscall, let alone calls it in a way that can be exploited.

I think a majority of systems security people, if asked, would say they assume an attacker with code execution on a Linux system can raise privileges.

I think in the land of people with ill intent to exploit such things they have more potential targets and security vulnerabilities than they can spend time exploiting. A given vulnerability may be terrible, but it might not coincide with something worth bothering with for a given person with ill intent. There's a factor of human choice / payoff at play.