Why do I require a Backplate for Graphics Card?

Solution
It's used for styling and sometimes it can help with cooling by acting as a heat sink on some of the components that are exposed on the back.
The backplate is usually just for looks. In single card setups it can yield better cooling but in SLI setups it will work against you.
BTW you wont really see the backplate in your case anyways so it's kind of a waste of money in my opinion.
 
The backplate is what keeps the card in the case, it has the screw mounts or where the screwless grips grab on to.

Do not use a video card if it's not mounted in the case like that, anything over a very cheap light card will not be held in place by the PCIe clip and even a small card can easily pop out of the slot when the case is moved or hit. We had some guy at work put on the backplate backwards in a radiology computer, never screwed it into the case, and he burned out a $500 card when it yanked out of the slot.

It also keeps dust out of the case.

See bellow, if you remove the backplate how are you going to mount the card in the case solidly? The screw connections are on top of the backplate.

GamingGraphicsCard-300x220.jpg
 


That is not what he is referring to when he says backplate. He is talking about a backplate for the back of the PCB, some cards have it and some don't.

For example: https://www.google.com/search?q=graphics+card+backplate&espv=2&biw=1280&bih=1318&source=lnms&tbm=isch&sa=X&ei=CRocVZKkKLj8sATSmoCQDQ&ved=0CAcQ_AUoAg#imgdii=_&imgrc=SP3q8Un0RbuvQM%253A%3B2oHQ23grySu6WM%3Bhttp%253A%252F%252Fwww.maximumpc.com%252Ffiles%252Fu69%252FEVGA_GTX_480_Backplate.jpg%3Bhttp%253A%252F%252Fwww.maximumpc.com%252Farticle%252Fnews%252Fevgas_newest_fermi_card_sports_backplate_custom_io_bracket%3B405%3B250
 
There's some evidence that a backplate traps heat and reduces thermal performance.

Quote:
"... Nothing keeps the heat from dissipating from the board’s back, which shows once again that backplates are pointless, as they are counterproductive for heat dissipation due to causing the heat to accumulate behind them. They sure do look nice, though."
http://www.tomshardware.com/reviews/nvidia-geforce-gtx-960,4038-10.html
 
The backplate is for style and could protect the back of the PCB. For example, if you had a liquid cpu cooler and it leaked, it would probably drip on your graphics cards, which is perpendicular to the motherboard. A backplate would protect it.
 


And who started calling that a backplate? Confusing terms now, backplates were always the part of the cards that were facing the expansion slot cut outs. See #8 here https://books.google.com/books?id=d-4DWu2tFu4C&pg=PA70&lpg=PA70&dq=computer+card+backplate&source=bl&ots=vGKYmqSjTs&sig=TkfEKAb04UPb1dn-LlCaDunw0dA&hl=en&sa=X&ei=-XwcVf3iMveQsQT6xILgDQ&ved=0CI8BEOgBMA0#v=onepage&q=computer%20card%20backplate&f=false Which is why it was odd to me that people were saying it was for style since that's the part that holds the card to the case!