Firstly, it's mainly Thai's who have "Red Boxes", so its not really intended to monitor Farangs. The face value benefits are: i) That the Police keep an eye on your property, ii)Sends a message to local robbers and thieves that you are "protected", and to neighbours that you are one of the good guys who support the Police.
As per previous post, in my opinion, it is the less obvious benefits that make it worthwhile.
It is not compulsory, I know plenty of cynical farangs and economical Thai's who've declined the service. Of course, it's usually the same farang who complain about lack of Police response when they get burgled.