If it can be rooted by you, it can be rooted by someone close to you, at which point it can be modified to install competent spyware tooling that hides that it’s rooted. Women who have been stalked by their exes will be quite familiar with the risk this poses. So will people who need Tor Browser to keep them safe from their governments.

I’d accept this as fine if I had to order it rooted from Google in hardware, so that the bootloader could show an unskippable “This is a rooted device and lacks critical security protections against malware attacks” warning.

Sadly, that’s not currently on offer. While your needs are legitimate, offering rooting in software on consumer-facing devices is more dangerous than they can afford. To me, the harm that comes to others isn’t worth it.