We think it is because the law regards addiction as a chronic illness, which will remain of substantial and permanent effect, even if the individual should find or be helped to find the strength to beat the problem.
This status does not mean that substance abusers can automatically expect to receive services, no matter how they conduct themselves, however. The authority is entitled to apply reasonable conditions as to non-use of substances causing the problem, as a condition of access to specialist facilities. If the individual cannot abide by those conditions, whatever help he is provided with, then the authority is entitled to treat such persons as persistently refusing a service, and hence itself as discharged from a duty to provide, at least for a while, notwithstanding that the need is still there.
The Care Act makes eligibility for publicly funded help turn on having needs related to a mental or physical impairment or illness. That problem has to cause an inability to achieve across domains in the national eligibility criteria regulations and causing significant impact for wellbeing.
If one is determined to pursue a lifestyle of misuse of drink or drugs, one could be said, objectively, to be someone whose difficulties are not rooted in physical or mental impairment – it would be different if one’s inclinations had caused some such problem independently of course. But one could also be assessed as conveying by means of one’s conduct that the impact of the inability to achieve is not such as to be significant enough for the person to try to help themselves.
Of course, a finding of misuse, or a formal diagnosis of addiction, could also be regarded, rationally, as indicating that the person literally can’t be expected to sort themselves out without help. That is when Public Health cessation services might be tried by way of prevention and reduction, first, or in the most serious cases, the assessor might take a view that the person lacked mental capacity with regard to recovery, which might make it more probable that they might be found eligible and given the chance of some tailored bespoke support in one setting or another.