It's a subtle technical issue that may be relevant to people using non-standard power supplies – when the power supply is turned off (or powered down), the unit detects this and performs some house-keeping. If the voltage ramps down too quickly, there is not time and problems may result.
I only mention this as an example of reasons why power supply choice is not as simple as it may appear.
Obviously, people are using other power supplies, and if they work well, best of luck to them, but we can't be responsible for the results.
