Homebrew now runs `brew update` before every `brew install`, no? That's how it gets in the way, you just wanted to install a thing, and now you are stuck waiting for `brew update` -- which I feel takes longer than it used to?
(You also may be confused between `brew update` and `brew upgrade`. I know I often am!)
I do not think it was a wise decision to enable auto update on `brew install` as long time users expect `brew update` and `brew install` to be two separate steps (as it was for years) and because Homebrew no longer operates like `apt` and other package managers.
It makes sense semantically to me, and would be fine/preferable if `brew update` only took a few seconds to complete.
Cause otherwise I'm not necessarily going to remember to brew update ever, and am going to be getting old formulae. I think I'm not alone, I suspect this was done because too many users were never updating.
I am not super familair with how apt works, but I think the "workflows" of brew are already different than typical apt uses, with continuous incremental releases, and users expected to stay up to date with them -- things aren't necessarily going to keep working (installing properly) if you never run `brew update`, and I think many users were not.
I do want `brew install` to get me the latest formula for the thing I'm installing.
The problem is when it can add several minutes to a `brew install` invocation, interupting my ability to get on with my business.
But good to know about the env variable so at least I can choose which tradeoff I want!
(You also may be confused between `brew update` and `brew upgrade`. I know I often am!)