It is unlikely the entire populace are on benefits. Many will have taken the chance to do something else, even if it means leaving settlements created for the express purpose of supporting the now-defunct mines. There are lots of people doing interesting and rewarding jobs in nice places who are jolly glad not to have had little choice but to follow their fathers and grandfathers down pit.
Railways replacing canals are a classic example of changes which caused problems for the people involved, but long term benefits for society. Should we give up our motor cars to support farriers? Unplug the internet so that boys can once again be paid a few pence to carry messages?
Few people actually want working class jobs: given half a chance the working class man will become middle class. The pit/trawler/mill is good for _other peoples'_ children, but we want our own kids to do something better paid, safer, or with a bigger future.
At various times my grandad was a foundry worker, docker, soldier and builder, and he made damned sure my mum (FWIW), and then my brother and I wouldn't be any of those things.