The ones I taught were resitting GCSEs or taking A levels that weren't on offer in their schools. Some were slightly mature students who were making up for leaving school early, and others just hadn't fitted into the school environment. There were some 'Adult Returners', mainly women who'd had children very young and wanted to go back to the workplace because their husbands were unemployed, and a few men who had joined the Armed Forces when they left school, had served their four years and needed a new direction.
The ones I taught weren't on an employment scheme - maybe it was EMA? There were things like hairdressing and car mechanics in other departments, but the one I was in was a bit like a sixth form for less conventional students. It's all so long ago it's hard to remember, but it was very rewarding, and I missed them when I moved to work in HE, as that was much more predictable.
The amount of money involved was enough to make a difference to struggling families though - particularly as (I assume) Child Benefit will have stopped so their budgets would have taken a hit when the students left school.
As I said, the college was in a deprived area which had lost its industrial base, so there were few alternatives for them - YOP schemes paying buttons or taking/resitting basic exams was about the extent of it. They couldn't claim benefits in their own right, I believe, whereas I think school leavers can do so now? I do remember that we spent a lot of time on attendance registers, and mothers were very keen to let us know if their children were unable to attend so they could get an authorised absence mark, and their money wouldn't be affected.
I'm not saying it was a panacea - actual jobs at the end of it would have been far more impactful - but being in college and getting qualifications was better than hanging about taking drugs, even if for many they were just deferring doing that for a couple of years.
Some definitely benefited from it. Years after I left I came across a chap who had been a GCSE resit student in a senior role in the university I worked in. Many of the women 'Returners' went on to get degrees. That often led to their marriages failing, but they were at last in a position to support their children when it happened, and I'm not saying there was necessarily cause and effect at play.