I agree with Flossie and have done a job that involves going into people's houses for social care / charity reasons.
But I can think of reasons that might suggest poorer famillies are MORE likely to have a messy house- but the main one is because the same issue can cause a struggle to cope and poverty: depression, MH, LD issues...... above threshoild for social input but below most people's definition of coping.
Not to mention people trying to hold down a part time job, raise a family and maybe care for a family member, and similar scenarios in all their permutations.
And also the simple reason that in my hugely relevant experience, those people who are poor are more likely to be picked up anyway, have an education or speak nively and youa r eunlikely to get services- as I have elarned to my cost as a carer whose every request for help is met by a wave of the SSD report saying 'Mum is educated and will cope'.
What can anyopne do anyway? Grandad lives in squalor; he is 91, Mum goes when she can to help, as does one of my Aunts and I try to when I am back home, but they can only do so much. Social workers are involved but as they say, unless he agrees to help (he has accepted 30 minutes of personal care but refuses anything else including sheltered housing) they are powerless.