Comment by VerifiedReports

Apple's window management has always sucked, with the absurdly crippled resizing being a longstanding embarrassment.

Into the 2000s, the only way you could resize a window on the Mac was to drag its lower-right corner. That is it. NO other corner, and no edge. So if the lower-right corner happened to be off-screen because the window was bigger than the screen, you were kind of screwed. You had to fiddle with the maximize & restore gumdrops to trick the OS into resizing the window to make that ONE corner accessible. Then you had to move the corner, then roll all the way up to the title bar and move the window, then roll back down to the corner... until you had the window sized and positioned as you wanted.

When Apple grudgingly added proper window-resizing, it made it as obscure as possible. Since Apple remains ignorant of the value of window FRAMES, there is no obvious zone within which the resizing cursor should take effect. There is no visual target for the user. This has always made an important and fundamental part of a windowed GUI a ridiculous pain in the ass on Macs.

And as the author here notes, it has gotten even worse. Not only will the window often refuse to resize, but you'll wind up activating whatever app lies behind the window you're trying to resize... hiding the one you were dealing with.