There are many genuine people who are unable to work due to ill health, and plenty of them get shafted by the disability assessors, and forced back into a job market that they’re just not able for.
But I’ve been a GP for nearly 30 years and I’ve seen many patients for whom the default is going “on the sick”. I’ve seen whole generations not working. Kids grow up seeing neither parent work, and as soon as they leave school they come for their sick note, for anxiety, fatigue, headaches etc. Of course they go through the investigations and treatments but nothing cures their ailments in the long term, because their expectation is to never work. They then go on to have kids who do the same.
I’m not saying these people have lovely lives - they certainly don’t - they live on benefits, often in poor quality housing, with very little to enjoy. In fact, they would almost certainly feel happier if they did work, had a purpose in life, got remunerated for doing something beyond simply picking up their sick note every few weeks. But benefits and unemployment is all they know and all they’ve seen, so they stay in their comfort zone.