The OP makes an entirely reasonable point, that the unemployed are being treated as if they are criminals. It's horrible. There are more than 2.5m unemployed. Does anyone seriously think there are jobs available for all of them?
And it is also true that people on the work programme are less likely to get a job than those who are job hunting under their own scheme. This scheme is costing us money, cutting jobs and keeping people out of work, not helping them into it. The only reason it exists is to punish the unemployed - picking on the victims of this government's failed economic policies.
Why should big business get free labour at the expense of taxpayers and the unemployed? At the expense of job opportunities? Because while the OP and people like her are working in shops, the companies need fewer workers, not more.