That would open them up to hundreds of copyright infringement claims!!!
Even 4'33" of silence might!
Were I a member of staff, or even a frequent user who doesn't want his own music, I'd hate having to listen to white noise for extended periods.
They play white noise in my building at work and, your first week you really notice it but, once you get used to it being there you don't notice it all.
Except maybe when something happens and it turns off and then it's so loud that you wish it was on again.