For the convenience of users, appliance manufacturers have standardised on two plug fuse ratings- 3A & 13A and adopted appropriate flex sizes.
For appliances up to 700W a 3A fuse is used, for those over 700W a 13A fuse is used.
The fuse in the plug is not fitted to protect the appliance, although in practice it often does this. Appliances are generally designed to European standards for use throughout Europe.
In most countries the plug is unfused. If an appliance needs a fuse to comply with the standard it must be fitted within the appliance.
The fuse in the plug protects against faults in the flex and can allow the use of a reduced csa flexible cable. This is advantageous for such appliances as electric blankets, soldering irons and Christmas tree lights, where the flexibility of a small cable is desirable.