You genuinely can’t imagine why someone wouldn’t want to live somewhere other than it being dangerous? That alone proves that you know nothing about life outside your own bubble.
The most obvious reason is lack of opportunities as a pp talked about upthread. The schools are glorified holding-pens until the children are turfed out to the jobcentre.
Since the industries were decimated in the 80s there’s no real future for them. There are no jobs other than part-time NMW jobs for those with no qualifications, and even those are few and far between. There are very few apprenticeships available. The lucky few will move away as soon as they get a chance, and the ones that remain are left to rot.
Life expectancy for men is almost 10 years lower than UK average due to poor lifestyle - drug and alcohol use, smoking and poor diet.
There are no amenities. Things like libraries, SureStart centres, youth clubs, adult education centres etc were all closed down during David Cameron’s austerity government after lots of these areas enjoyed a brief resurgence under the New Labour government. Shops, local markets etc have also closed down and the high streets are boarded up apart from the takeaways, vape shops and off-licences. Most of the pubs are long gone. These are all places where people used to work, and those jobs haven’t been replaced.
The council spends no money to improve these areas. Grass and weed cutting, graffiti removal, proper street lighting and litter clearing are luxuries of years gone by. As a result these estates are squalid and depressing. In the town I grew up in, a third of adult residents are on anti-depressants, the rate highest in the country.
The average house price there is £174,000. But for the sake of a cheap house, your children would be growing up there. Would you move your children somewhere like that?