RAM is used by an operating system and managed. You may use 11/16 GB at once, but someone could browse the internet with the same tabs at 3 or 4 GB and be fine. Hell, they could at 2GB and be fine.

The operating system plays a huge role in memory usage, many modern ones cache indiscriminately, preload most used applications, etc etc

Comparing RAM usage is almost apples and oranges these days, unless we're talking similar setups.