As others have mentioned, /usr/local may be a fairly standard place to put stuff, but homebrew's permissions model changes the way /usr/local works. Additional

As others have mentioned, /usr/local may be a fairly standard place to put stuff, but homebrew's permissions model changes the way /usr/local works. Additionally, /usr/local is used by other applications, and there's no way to ensure that it isn't written over by them or by homebrew when installing or upgrading software. Putting homebrew in /opt/homebrew means that you can have a systemwide directory that is self-contained, can have a working unix hierarchy underneath and should work. Putting homebrew in ~/.homebrew/ lets you have a user-specific directory that is self-contained with a hierarchy underneath. In an ideal world, homebrew would use something like /opt/* for systemwide hierarchy and ~/.homebrew for user-specific hierarchy. We don't live in an ideal world, so we just have to make do with fudges to /usr/local permissions for now.