The brain is used to a certain levels of noise. The brain can learn to pay no attention to the sounds of tinnitus if it has something else to work on. They help the wearer sleep deeper at night.
The wearer might experience the residual inhibition when the device is turned off for the night. Otherwise the amplification can be turned off while leaving the masking sound turned on. That was three years back now, and I couldnt be happier that I incidentally bumped into that woman.