In the first place bitcoin was created to minimize the disadvantage of a physical currency. Physical things are so expensive to maintain. From printing to transporting there is so much expenses you have to consider. While electronic cash can be instant, cheaper to maintain and not easily counterfeited.
Although cryptocurrency (or as this thread called Electronic money) can not fake by anyone, but you have to remember, the fees to keep this system running is not small as you said. How many money the mining farm must pay for electric bill and maintenance device? Without blockchain and decentralized system, that currency can fake by others.