No disrespect but I fixed a small discrepancy for ya. When you add in the idea that Windows Store apps are designed not needing to be closed all of a sudden this makes the Windows Store app taskbar pretty useless. Do you close the apps to make the taskbar useful or do you leave the apps open because you are not supposed to have to close them?
It's not useless though, it just isn't intended for the purpose you're trying to suggest it should be. It's more a MRU list for Metro* apps. Even if you "close" them to try and pretend that it is showing "running" apps, reality soon breaks when, for example, someone sends you an IM (for example) and the Messenger app which wasn't "running" pops a notification up on screen (and still doesn't appear in the MRU list till you actively open it).
You have to let go the idea that trying to somehow use "running" applications as some sort of mental "what am I doing" list makes much sense - even the old-school Taskbar was pretty rubbish at doing that, because it could only ever give you a single "grouping" (so no real-world multi-tasking for you) and couldn't persist beyond reboots etc. You can probably far more usefully manage your time and thought processes with a Metro* to-do list style app pinned to the side of the screen than you ever could with the Taskbar.
*Yeah, I said it. Sticking to that till a less silly designation happens