Crack and heroin addicts spend hundreds of pounds a week, more commonly, a day.
Benefit payments just make them have a few easier hours.
There are literally no crack or heroin addicts solely funding their habit from benefits.
They never have money for more than a few hours. It's a bottomless pit, they'll never be enough. And once the benefits run out they'll steal, rob, lie, cheat, defraud and sex work, abuse, and exploit.
Crack and heroin addicts already commit most of the burglaries and robberies in the UK but sadly, addiction is powerful and many people even when offered treatment, don't want it or find it too difficult or just don't want to change enough to do so.
Drugs feel good. Same as alcohol. They effect dopamine and serotonin receptors and because of that, if you do them very regularly, you will very regularly feel not as good when you're not doing them, so you want to do more.
That's what addiction is and how it works on a neuropsychiatric basis.
Most of the chronic addicts you see on the streets are receiving an alcohol or drug service and have been through rehab once or multiple times.
Nothing recovery can offer will ever feel as good as using, which floods the brains neurotransmitters.
That's why people keep doing it. It's a fallacy that all these addicts are crying out for help which isn't available. It's available for most people and for the people that it isn't, they're blaming the system and saying 'oh i'll stop when...' but even inpatient rehab services have really bad relapse rates.
Because there's nothing to compare to using. So it comes down to the person choosing to prioritise their health, family, relationships, safety and wanting to be a productive member of society.
Many don't.