I have never personally had home security systems in any house in which I have lived. We have not even had our smoke detectors working one hundred percent of the time to be truthful. I guess it is because I have never had all that much in the way of valuables to take. The only thing I would need home security systems for would be my lovely girlfriend and she carries a knife on her anyway so I do not think it would add much in the way of assured safety. She is already a sort of spring loaded knife wielding security package in and of herself.
Home security systems would definitely be a worthwhile investment for those who participate in the uniquely capitalist practice of conspicuous consumption. Barking dogs and motion sensing flood lights are good beginnings but have serious drawbacks when compared against high end home security systems. You have to feed the former in order for it to be beneficial. The latter simply lights up and does not do much to deter a potential vandal or thief.
Professional home security systems are the ideal combination of safety and simplicity. Companies which specialize in home security systems make their money by providing quality service. Otherwise they would not be in business for very long given the broad spectrum of other options available to the homeowner. A savvy homeowner can install his own home security systems but would not have the support of a third party to be around when they are indisposed or not present.
Home security systems protect more than just valuables. They would have to grant peace of mind for inhabitants of the house to be truly worthwhile.