A modern server can be power cycled remotely, can be reinstalled remotely over networked media, can have its console streamed remotely, can have fans etc. checked remotely without access to the OS it's running etc. It's not very different from managing a cloud - any reasonable server hardware has management boards. Even if you rent space in a colo, most of the time you don't need to set foot there other than for an initial setup (and you can rent people to do that too).
But for most people, bare metal will tend to mean renting bare metal servers already configured anyway.
When the first thing you then tend to do is to deploy a container runtime and an orchestrator, you're effectively usually left with something more or less (depending on your needs) like a private cloud.
As for "buying ahead of time", most managed server providers and some colo operators also offer cloud services, so that even if you don't want to deal with a multi-provider setup, you can still generally scale into cloud instances as needed if your provider can't bring new hardware up fast enough (but many managed server providers can do that in less than a day too).
I never think about buying ahead of time. It hasn't been a thing I've had to worry about for a decade or more.
All of this was already possible 20 years ago, with iLO and DRAC cards.
And, lets face it - arent you already overprovisioning on the cloud because you cant risk your users waiting 1-2 minutes until your new nodes and pods get up? So basically the 'autoscaling' of cloud has always been a myth.
The bad old days of begging an IT ops person for a server, and then throwing a binary over the fence at them so they can grumble while they try to get it running safely in production... yeah, no, that doesn't have to be a thing anymore.
The "we" you speak of is the problem: if your org hires actual real sysadmins and operations people (not people who just want to run everything on AWS), then "you" don't have to worry about it.