Ah yes, the same crap about what's being "used" without the entire system context being considered. Because as we all know, simple numbers tell the entire story all by themselves.

The system and apps will use what's available if you have it. That's what you want, unused RAM is wasted RAM, and there is zero reason not to use resources that are readily available. The system automatically caches and preloads things like files and applications you tend to use at certain times of the day so they load faster when you do access them. This is used memory, but it is also readily available for literally anything else.

All of those apps know you have plenty more memory readily available if they want it, so they will fill to use whatever they want and won't attempt to do more than basic memory management. Once the active resource usage fills, both apps and the system itself will begin more aggressive memory management. Until then, there's no reason to.

Remove RAM until you have 16GB, run those exact same things and you will almost certainly see under 16GB of usage.