No, because then the unit would be on all the time and you'd have to manually shut the unit off.
The memory (yellow) wire should be wired to a constant 12V source, as this allows the unit to retain all of it's stored settings such are radio presets, etc.
The power (red) wire needs to be wired to an iginition controlled source, so that it only receives power when the key is turned to ACC or On/Run, this way the unit will automatically turn on when the car is turned on (or to accessory), and turn off when the car is turned off.
So..yes, technically you "could" wire them both to a constant source....but it isn't the proper way to do it.