Probably for convenience and stability. Linux on the desktop (or on a laptop) has its share of bugs and odd behavior still in 2020.
But MacOS does handle low memory conditions much better than Windows does.
MacOS (on apple hardware) does have the benefit of optimised fan curves and undervolted CPU profiles which would be hard to replicate in Linux though.
Catering for edge cases like; when closing lid, it should not go to sleep, with external drive connected and mounted, it won't boot if that somehow disappears, Apple remote cannot easily be disabled (there's one used in the room, and it's picked up by the laptop constantly).
I also have occasional issues where the trackpad stops working after a period, and requires a reboot to fix. More of an X issue I believe.
Couple ideas, for what little they may be worth. Grub might be installed on the wrong drive. Or, if you’re getting past grub, look up systemd’s nofail option for /etc/fstab.
Interesting, my work machine runs a linux vm on a windows 10 host. It regularly uses 95 to 96% of my 16GB RAM. When this happens Linux grinds to a halt yet Programs running on Windows are still usable. MacOS must be amazing,