I don't think we know the whole story! If the repair required is a landlord's responsibility from law or tenancy, then landlord has to repair. S.11 Landlord and Tenant Act 1985 is the obvious starting point.
Posters might also want to read Warren-v-Keen from 1954 where the late Lord Denning laid down in common-law what a tenant can be responsible for and where phrase 'use the dwellling in a tenant-like manner' comes from.
My fear is that has money/resources tighten-up some social landlords will try and 'get away' with not doing repairs for which they are responsible. The reduction in legal aid will make this more possible.
I suggest anyone worried about this should check the law, their lease or tenancy, the local CAB and ask 'tenant scrutiny' to investigate. That's what they are for!