Mr. England, welcome to the forum!
Simply speaking (it can get very complex), amps x volts = watts. The same amount of power can be delivered by a high voltage at a low current as by a lower voltage at a higher current. There's a reason we use each.
High voltage requires heavier insulation; high current requires larger conductors. Insulation is cheaper than conductor. Plus, voltage drop is a function of current, so high voltage is used to transmit power over distances.
Look up at a utility transformer on a pole. Note that the primary, the wire attached to the conical insulator on top, is relatively thin. Now look at the heavier wires attached to the secondary terminals on the side.
The small primary conductor is able to deliver the same amount of power (in watts) as the larger secondary conductors. The same thing is done again inside the charger; more current is available, but at a lower voltage.
One more example: look under the hood of your car. The battery cables and the spark plug wires are about the same diameter. The battery cables are almost all conductor, and the plug wires are almost all insulation.
Note, too, that the wires feeding the ignition coil(s) are probably 18 gauge or so. That's because the current required at 12v to induce the spark voltage (which is in the 25-kv or higher range) is very low.