The Efficiency of your speakers..
The efficiency of the drivers in any speaker is extremely important. If there is no music playing yet there is background noise from the source audio, or line noise, the drivers are essentially working. When the music resumes that noise is no longer audible but it is still being produced by the driver at the same time as the music is being produced even though the noise is now in-audible. If the driver has to produce the music and the noise, the efficiency of the drivers ability to produce optimal sound goes down because the driver is producing the unnecessary noise, in turn causing a frequency clash. The more noise/hum/buzz/clicks that we can remove during the mix stage the more efficient our speaker drivers will be at producing a clear defined sound.
Simply cutting the noise out where it is audible will not do. As the noise will still be present in the background of the intended source. There are many noise reduction techniques that can be used to remove noise while maintaining the original sound. Noise reduction/removal can be done via plugins and hardware after production, however making sure there is no noise in the the recording at the recording stage is the best practice. The thing to remember is that any speaker driver's ability to reproduce accurate sound will be based on everything that is feeding it even electrical noise. If the driver is making a noise it is working and Therefore it is
extremely important to have a clean signal at all times as well as a clean power signal so that the driver can be as efficient as possible...