Why do power systems only use AC and not DC to generate electricity?

You should know that the wire is resistive, the current through the wire, the wire will heat up, wasting part of the power hypothetically, a 220V DC transmission line, if the resistance of the wire is 1Ω, the transmission current is 10A, then the heat loss power is 100W, these heat losses is the wire white heat, the loss of power, in the long run will cause how much waste? However, if this line through the alternating current, you can use a transformer at this end to step up the voltage, the other end using a transformer to step down the voltage, the middle of the high-voltage transmission, assuming that the transformer will be 220V up to 2200V, the current will become 1A (the law of conservation of energy, the conductor to deliver the power remains unchanged), then the heat loss becomes 1W, if it rises into the 22,000V, the conductor heat loss becomes 0.01W, using the Alternating current, how many times the voltage is increased, the heat loss will reduce his square times, that is to say, the voltage is increased by 1000 times, the conductor's power loss is one millionth of the previous one, the country will save a huge amount of money for this.