On a VM OS like Linux, Apple OS, Windows, all RAM should be used, even if for a trivial purpose.
Why? That's what a VM (virtual memory) OS should do.
If you feel this is wrong you have to find a non-VM OS.
My name's Huy. I use windows 10 on the computer. When it comes to windows, it only accounts for 40% of the ram, and after surfing the net the ram is 99%. Then when I shut down firefox then the ram capacity is 66% occupied even without using any software.
My PC: Core I3 7100, DDR4 8GB, VGA Gigabyte 5770 1GB, SSD 120GB, HDD Western 2GB.
Can you help me?