Probably because a lot of people feel like they need exclusive fullscreen for best performance and/or latency. But in reality borderless fullscreen is exactly the same when games use the DXGI flip model. It bypasses DWM (the compositor) to render directly to the display when only the game is visible and seamlessly allows you to switch to other windows. You can even disable Vsync and it will allow screen tearing when bypassing DWM.
Still, I’ll admit that Minecraft full screen on Mac is even worse than almost all other games.
I like to play games like ARC Raiders using that setup. Works perfectly fine. Sure it sucks that I need Windows at all for it, but SteamOS isn't an option yet due to my 3090
I’m not really a fan of the way it’s a three finger swipe sideways to leave and enter the full screen either.
I’m pretty sure I have had at some point issues where putting my cursor at the top of the window erroneously shows the menu bar within certain types of games.
Not sure if I’m remembering right, it’s been a while since I’ve tried playing games on Mac.
The menu bar is supposed to appear with the cursor at the top of the screen. I have also encountered issues where it doesn't properly hide until you bring your cursor back in order to take the cursor away again and then it hides. It's a quirk but I sort of understand why it happens and it's just a small glitch to me.
Conversely, using borderless windowed mode instead of native fullscreen on macOS adds rendering latency due to the Desktop Window Manager (DWM) compositor. The latter is 'doing it wrong' and has the lag people don't like.