I'm sure you could, vampirequeen.
No, I can't give you hard evidence, because it's based on conversations I had with ESA claimants years ago, when the DWP sent me on courses. There's me for a start. I know I can't do a full-time job. I did actually try, but struggled to finish my contract, which is when I decided to become self-employed. I now feel in control of my work and, if the worst comes to the worst, I can turn work down.
Most of the people on the courses I attended spoke of not being able to work not because they couldn't, but because they would lose benefits and it wasn't worth it.
There was somebody on GN (can't remember who) who wrote of losing about £100 a week if she were deemed 'fit for work', because it would be means tested and she had other income. That's a considerable amount of money to lose for perhaps doing a couple of hours work a week. My argument is that people (like me) who can only work in a limited way should not fall off a financial cliff edge.
There are also people with terminal illnesses who want to work for as long as possible. My best friend had cancer, which spread to her spine, so she had to use a wheelchair. She was a teacher and her school was incredibly supportive. It created a job for her working one-to-one with special needs children and allowed her flexible start and finish times, so she avoided the hordes. She worked to the end of the Autumn Term and died during the Christmas holidays. Her attitude was that she was living with cancer and she wanted to carry on doing what she could. She saw no benefit in staying at home and waiting for the grim reaper. I think the DWP, NHS and employers should support people who want to do that.