Hah, I still use laptops with 2G and 4G :) They work perfectly fine when you know what you are doing. But running Java with 16GB pool does not fall in that category. The same holds for small cloud instances.

Admittedly even with a C program the size of a problem requiring 16GB might not run well in a 2GB machine, but the fact remains that Java applications are often much more memory hungry than comparable C/C++ implementations. And if you have the memory they will just use it without any Xmx. That sounds really like computing in the 1960/70s that you need to allocate memory in advance. (I'm old enough to have seen such stuff, although not when it was new.)