The benefit of having unused RAM is that every program you are using can remain in memory for quick multitasking access and when you go to launch a new program it can be loaded into that unused RAM without unloading any of the currently running programs. What part about that is a misunderstanding? Would the user be better off if the application in focus aggressively reserved RAM it didn’t need to slow down every other running application? Because that’s what Photoshop does