The vast, vast majority of benefits claimants in this country are in some form of paid work, and receive top up benefits such as tax credits, to supplement their poor wages. Many families receive benefits because one member of the family needs additional help, such as a child on dla, or an adult who is short or long term unable to work. For families, benefit claims are joint claims, which makes things more complex still.
For example say I work 40 hours a week, earn a crap wage, and have a dh with chronic treatment resistant mental health problems (so not a visible disability). We jointly claim benefits as a result. Are you seriously suggesting that on top of my 40 hour week, caring for my children, caring for my husband when he is in a bad spell, and generally keeping the house and family going, as the only family member fit enough and old enough to work, I should be picking up a few hours of enforced 'voluntary' work in exchange for receiving the benefits which allow me to go to work in the first place? It's clear you have no understanding of the benefits system, and your suggestion, OP, is insulting on more levels than I have the time to point out, for all of the aforementioned reasons.
What would make a difference and truly help people move away from benefits is a decent living wage, affordable childcare, affordable housing, genuinely flexible working, access to education throughout life, and enough jobs, not just to go around, but to match the skills people have available, or alternatively upskilling people to match the jobs needing filled.
One other thing. There are more unemployed people in the uk, than there are jobs. Of those vacancies, 100,000 are nhs jobs. Which no one either wants to do, or is qualified to do. Hundreds of those vacancies are teaching jobs, as people leave the teaching profession in droves. There are 1.3 million unemployed people, and of the 750,000 jobs, a huge chunk are jobs where people are fleeing the professions because they have been run into the ground. It's not as simple as number of jobs equals number of people.