The outlet does not supply 16 A because it does not behave as a current source but as a voltage source. Imagine the socket would always try to supply 16 A, then you switch off your toaster, what would happen ? The current needs to flow so the socket would increase the voltage to several thousands of volts until the current just sparks over ! Hmm, that does not sound very practical to me.
So instead the socket just maintains the voltage. If you have a load of 1000 W, at 230 V that would be 4.3 A. Ohm's law then states that it has a resistance of V/A = 230 / 4.3 = 53 ohms. When you connect this 53 ohms load to the 230 V mains only 4.3 A will flow and your load will consume 1000 W.
Now what would happen if you would connect a load of 230V / 23A = 10 ohms.
Then 23 Amps would flow and the 16A fuse would blow to protect the wires !