Earlier quoted context omitted.
All Google phones and Android One devices have unlockable bootloaders.
Rooting the Pixel 2 (I haven't tried the other Pixels) is not trivial for the average user, it still involves downloading third-party software and doing stuff on the command line. I had hoped that the pure-Google devices would have just had a switch: "I am now root," but alas it wasn't to be.
https://source.android.com/setup/build/running#unlocking-rec...
You're correct it's not trivial for the average user, but the average user should also not have a rooted device (nor does the average user even want a rooted device).
Is the learning curve perfect for the semi-advanced user? Probably not. But third-party software also fills this gap just fine. I don't think Google should be a required party here. They do provide officially supported tools & documentation for the process itself (and those tools work on all major platforms at that), just not a shiny GUI to do it. I think that's a reasonable point to be at.