Every other piece of household equipment seems to come with its own 6- volt transformer these days. A glance at the tangle of cables under my desk reveals transformers for two mobile phone chargers, halogen desk lamp, answering machine, calculator and cordless phone. Elsewhere are a couple of vacuum cleaners, electric drill and screwdriver, more cordless phones and a doorbell. Then there are shaver points in the bathrooms and chargers for garden tools and golf trolleys in the garage. This ignores those other items (PCs, radios, clocks, which probably have their own in-built transformers).
All of them cost money to produce, sit there consuming electricity, generating heat, electromagnetic-magnetic fields and goodness knows what else, tripping one up and probably constituting a fire hazard. How much simpler a second low voltage circuit around the house would be so that we could just plug these gadgets all straight in.