the addict-as-burglar sociology
Drug addicts driven to crime to finance their drug addiction are not often inclined toward violent crime. Violence requires all different kinds of energy, and most drug addicts like to expend their energy not on their professional crime but on what their professional crime lets them afford. Drug addicts are often burglars, therefore.
Context
The book opens Gately's arc with a small sociology of the disease as economics: violence costs energy the addict would rather spend on what the crime buys, so the addiction routes him into burglary specifically, and the residue it leaves in a stranger's home — the sense of being violated and unclean — is literally the addict's own condition tracked in on his shoes. Character and crime are both downstream of the need.