The majority of crime committed in the UK is usually drug-related. Burglary, muggings, robberies etc are all ways of funding an addiction and the more serious the addiction the greater the chance of these being accompanied by violence. There are people who are so desperate to have a ‘fix’ or are completely controlled by their addiction that will do anything to service this. If this means using violence then they will do so. In this case their needs have overtaken any thoughts of rational or civilised behaviour. They are not thinking of anyone else but themselves as they are consumed by their addiction.