You wouldn't want to give a lot of these people a job. But they probably aren't properly depressed, they are just lazy bums who want a sick note from their GP to get get more benefits. Because the GP is a lazy bum who cannot be bothered he gives them one.
So they are labelled depressed, get an excuse not to work, get more benefits, and they are happy.
A lot of people with genuine depression would love to work but the condition cripples them.
But probably in the minority, in this modern 'you owe me everything and I have to prove nothing' society anyway.