To exaggerate a bit, you could drive a carrier battle group though the memory holes and leaks in Chrome. I have freed up over 4 Gigabyte of system memory this way before. And seeing that total memory is now lower. Closing Chrome, then reopening it to the exact same tabs it had open before. This is easiest to demonstrate, by taking a long running Chrome session that has had a large number of tabs opened and closed. Rather that it does not properly release memory once a tab has been closed. The problem with Chrome, is not that it uses a lot of memory for the per-tab process isolation. Like Windows, it doesn't want to waste memory which could be improving performance and security, and once it goes background it doesn't use much anyway.) It looks like it's using a lot of memory, but really both isn't using all that much, and is using it for good reason. It uses process isolation to boost security, so has a lot of processes. (To address Lee Vann's point about Chrome above, it follows the same model. There's no problem here, your system's working well.
If Windows could avoid wasting the memory, it would have. That's memory which Windows can't use for architectural reasons, or memory reserved by an onboard video device. If you look at the block just under the usage history chart, you'll find that the "free" block, the tiny bit at the right, is quite a lot smaller than what it's showing as available. Cached blocks can be both "In use" and "Available" at the same time, for example! There's also things like the standby page list (which also contains cached disk objects!) and recent evicts, which exist in a limbo zone between in use and not in use. It's also a virtual memory system, meaning there are lots of types of memory, some of them should be counted as "used" and some of them shouldn't be.
Why waste RAM? It's one of the most precious commodities a PC has. You see, memory not used is memory wasted. There's either water in the bucket or not, so memory is either in use or not, right? In this model, a Windows system would almost always be 95-100% full. You seem to be thinking of a fairly naive "bucket model" of memory. You're inadvertently looking to cause yourself a problem, though. I'm guessing the answer is "no" in all three cases. Is the system slow? Does it crash? Do applications not run?