It's normal because unused RAM is wasted RAM. Generally macOS tries to keep RAM highly utilized. Things will be cleared out when needed. As long as your Memory Pressure graph remains in the green, you are fine and don't need to worry about the Used amount.
This seems to run counter to the whole design of the memory manager in the OS. But it should be noted that VM used isn’t the same as pages resident in RAM. So untangling what is going on in memory isn’t straight-forward.That is so not true. It will keep cached files as long as it can, preferring to swap to disk and compress memory before giving up cache, slowing down the system considerably. Doesn't happen on Linux.
Its very likely there’s a lot of memory mapped or shared data in there causing the VM address space to have a lot of usage. Real memory is the count of allocated pages associated with the process. Real memory is the one you should pay closer attention to if RAM usage if what you want to know about.My Windowserver is currently 14 GB, and it can't be purged. Real memory is 1.2 GB.