'Proceeds of crime' actions are sometimes carried out, even when the offender is known to be broke, because they allow future monies to be drawn upon.
For example, an offender might need to pay back many thousands of pounds because of the profits he's made from drug dealing but (because he's now broke from feeding his own habit) he'll only be required to pay back a nominal sum of £1.
However, once that ruling is in place, if the offender later comes into money (perhaps through winning the National Lottery or simply because his parents die and leave him their house) then that money can be taken from him to make up the shortfall.