Benefit differences.

If you have been on a means tested benefit for at least 26 weeks, you can expect some perks when you do succeed in getting a permanent job. A job grant, worth £250 if you have children and £100 if you don't is paid to you.
If you have been getting Housing Benefit and Council Tax Benefit these may continue for four weeks after you have started work, to tide you over until you receive your first pay packet. In some cases, Income Support may continue for two weeks when you are actually working, for the same reason. Income Support, remember, is a non-contributory benefit. If you've paid nothing into the system, you can get IS.
But what if you've been getting Incapacity Benefit? This is a contributory benefit. If you've never worked, you don't get it. However, if you're on IB, when you start work again there's no job grant for you, and no HB and CTB run-on.
I interviewed a claimant who had had a stroke, and wanted to do a college course to make himself more employable. (He was no longer able to do the job he'd had before the stroke, so wanted to retrain for something else). If he'd been on IS, he'd have got a reduction in the fees. As he was on IB, he had to pay the full amount. Or rather he didn't, as he couldn't afford it. So he never went to college, and was unable to make himself more employable.
Things like free prescriptions are also not available if you're on a contributory benefit.
Of course, if you're on IB it isn't means-tested, so you can have £5o,ooo.oo bank and still get it. However, not many of our claimants have much money in the bank, and if they did, it wouldn't last long if they were trying to live on IB.