Disk Utility provides the ability to erase the drive. Always been there? Yes, of course. Then, you boot into an installer and reinstall the OS.
User data? Yes, always been there. Delete the account from Users and Groups and away goes the account.
But! The Application layer remains—along with all of its trash, subscription-based apps, App Store (and, thus, Apple ID) purchases, and licensing issues—for the next user.
So, when we prep a Mac to be sold as used we need to erase the user layer
and the application layer. The only way to
cleanly do this is to wipe the entire machine and reinstall the OS. Or, if a user wants to prep their Mac to donate, hand down, or sell—and they want all of the data gone—they have to go through the same process. It is time consuming to the point of crazy, especially if they have slow internet and need to reinstall the OS.
"Erase all content and settings" on iOS/iPadOS has always made me jealous since it is so blooming easy and doesn't require a fresh OS install. Now, on the Mac, if we want to eliminate everything installed by a user it will be a one-click option that will require nothing more than a password to implement. All users get wiped, all user-installed software gets wiped, and all settings get wiped. Then, upon reboot, it's like the Mac was just purchased and the new owner can set it up however they choose.
Keep in mind that Find My Mac will have to be shut off prior to the wipe, but otherwise this
greatly simplifies a restore, sometimes by several hours!