System design and stability. On MacOS a lot is shared between applications compared to the average Linux app. Dynamic linking has fallen out of favor in Linux recently [1], and the fragmentation in the ecosystem means apps have to deal with different GUI libraries, system lib versions etc, whereas on Mac you can safely target a minimum OS version when using system frameworks. Apps will also rarely use third party replacements as the provides libraries cover everything [2], from audio to image manipulation and ML.
People who need 64GB+ RAM are not running 1000 instances of native Apple apps. They run docker, VMs, they run AI models, compile huge projects, they run demanding graphics applications or IntelliJ on huge projects. Rich system libraries are irrelevant in these cases.
This thread started as question on how MacOS is more efficient, not the usefulness of more RAM. In any case, you might still benefit from the substantial increase in bandwidth and lower system / built-in apps memory usage, plus memory compression, making 16GB on Mac more useful than it seems.
I can run apps with 4 distinct toolkits on Linux and memory usage will barely go past the memory usage of opening one Facebook or Instagram tab in a browser.
Compared to compiling a single semi-large source file with -fsanitize=addresses which can cause one single instance of GCC or Clang to easily go past 5G of memory usage no matter the operating system...
How is that different from plain shared libraries?