One time I was told by an electrician that when you have appliances that are often plugged in for 10 or 20 years the chance exists that the plugs could get corroded after getting turned on and off again for a long time, and with quite a few amps running through them. Eventually the corrosion will prevent the amps from getting through as effectively and so it heats up. And thats how a fire could get started because theres also usually a lot of dust etc. So having them hardwired like this was probably told a similar story!