It's a zoom button, not maximize. If you simply Shift-Click you will get the expected effect. There are half a dozen tools that will change the default behavior if you require it.
As for Shift-Click I tried it with Chrome and I thought you had made my day. However it didn't do anything different on Messages, nor Safari: it just stretched the window vertically. In my short survey of currently open apps, half were stretching vertically while the other was doing fullscreen. (be it Shift-click or plain click) Only Chrome acts differently.
The biggest problem with that is that developers make it work inconsistently.
If by "developers" you mean "Apple" then yes. I never use the "zoom" button because it exhibits apparently random behaviour.
I personally can't come up with a good reason not to just remove the green ball entirely.
Apple should remove the zoom button. It’s not necessary, more confusing than anything.
Wrong. They're from people who think every window manager should act consistently. This is decades of UI design and expected behavior being flushed down the toilet by a company for which NIH is religious dogma.
That Windows behaves the correct, expected way is an indictment on OS X, not its growing base of increasingly frustrated power users.
I don't see how that couldn't be turned entirely on its head? Windows is clearly the one ignoring the decades of UI design and expected behaviour from Apple, as from checking from screenshots, has been since at least System 3 — predating Windows 3.1. ;-)
Though, I agree that Apple seem intent in ridding themselves of powerusers and developers, which seems like a somewhat perverse set of incentives.
I still stick to my guns: the default behavior is insane. Focusing on one task (ie: one screen, window, app etc) at a time is the common use case, when I want to show two screens at once it's the exception. Current behavior is based on a philosophical concept of carrying through the "desktop" metaphor, and SJ's obsession with showing off his stacked windows, which mac was first to have, rather than on how humans actually want to use computers.